diff --git a/packages/browser/src/eventbuilder.ts b/packages/browser/src/eventbuilder.ts
index c3734c9c39e6..ef77a22ebcd8 100644
--- a/packages/browser/src/eventbuilder.ts
+++ b/packages/browser/src/eventbuilder.ts
@@ -65,15 +65,14 @@ export function eventFromUnknownInput(
 ): Event {
   let event: Event;
 
-  if (isErrorEvent(exception as ErrorEvent) && (exception as ErrorEvent).error) {
+  if (isErrorEvent(exception)) {
     // If it is an ErrorEvent with `error` property, extract it to get actual Error
-    const errorEvent = exception as ErrorEvent;
     // eslint-disable-next-line no-param-reassign
-    exception = errorEvent.error;
-    event = eventFromStacktrace(computeStackTrace(exception as Error));
+    exception = exception.error;
+    event = eventFromStacktrace(computeStackTrace(exception));
     return event;
   }
-  if (isDOMError(exception as DOMError) || isDOMException(exception as DOMException)) {
+  if (isDOMError(exception) || isDOMException(exception)) {
     // If it is a DOMError or DOMException (which are legacy APIs, but still supported in some browsers)
     // then we just extract the name, code, and message, as they don't provide anything else
     // https://developer.mozilla.org/en-US/docs/Web/API/DOMError
@@ -90,9 +89,9 @@ export function eventFromUnknownInput(
 
     return event;
   }
-  if (isError(exception as Error)) {
+  if (isError(exception)) {
     // we have a real Error object, do nothing
-    event = eventFromStacktrace(computeStackTrace(exception as Error));
+    event = eventFromStacktrace(computeStackTrace(exception));
     return event;
   }
   if (isPlainObject(exception) || isEvent(exception)) {
diff --git a/packages/integrations/src/ember.ts b/packages/integrations/src/ember.ts
index 811e8b4852f8..c31c5aebb809 100644
--- a/packages/integrations/src/ember.ts
+++ b/packages/integrations/src/ember.ts
@@ -58,7 +58,7 @@ export class Ember implements Integration {
         getCurrentHub().withScope(scope => {
           if (isInstanceOf(reason, Error)) {
             scope.setExtra('context', 'Unhandled Promise error detected');
-            getCurrentHub().captureException(reason, { originalException: reason as Error });
+            getCurrentHub().captureException(reason, { originalException: reason });
           } else {
             scope.setExtra('reason', reason);
             getCurrentHub().captureMessage('Unhandled Promise error detected');
diff --git a/packages/integrations/src/extraerrordata.ts b/packages/integrations/src/extraerrordata.ts
index de01df6605c0..5fc3bb2f319f 100644
--- a/packages/integrations/src/extraerrordata.ts
+++ b/packages/integrations/src/extraerrordata.ts
@@ -97,7 +97,7 @@ export class ExtraErrorData implements Integration {
           continue;
         }
         const value = error[key];
-        extraErrorInfo[key] = isError(value) ? (value as Error).toString() : value;
+        extraErrorInfo[key] = isError(value) ? value.toString() : value;
       }
 
       // Check if someone attached `toJSON` method to grab even more properties (eg. axios is doing that)
@@ -106,7 +106,7 @@ export class ExtraErrorData implements Integration {
 
         for (const key of Object.keys(serializedError)) {
           const value = serializedError[key];
-          extraErrorInfo[key] = isError(value) ? (value as Error).toString() : value;
+          extraErrorInfo[key] = isError(value) ? value.toString() : value;
         }
       }
 
diff --git a/packages/nextjs/src/utils/instrumentServer.ts b/packages/nextjs/src/utils/instrumentServer.ts
index c05fa9cac226..6dd28b66c6d8 100644
--- a/packages/nextjs/src/utils/instrumentServer.ts
+++ b/packages/nextjs/src/utils/instrumentServer.ts
@@ -227,7 +227,7 @@ function makeWrappedReqHandler(origReqHandler: ReqHandler): WrappedReqHandler {
           // If there is a trace header set, extract the data from it (parentSpanId, traceId, and sampling decision)
           let traceparentData;
           if (req.headers && isString(req.headers['sentry-trace'])) {
-            traceparentData = extractTraceparentData(req.headers['sentry-trace'] as string);
+            traceparentData = extractTraceparentData(req.headers['sentry-trace']);
             logger.log(`[Tracing] Continuing trace ${traceparentData?.traceId}.`);
           }
 
diff --git a/packages/nextjs/src/utils/withSentry.ts b/packages/nextjs/src/utils/withSentry.ts
index f7792070f400..3f7a737904e7 100644
--- a/packages/nextjs/src/utils/withSentry.ts
+++ b/packages/nextjs/src/utils/withSentry.ts
@@ -39,7 +39,7 @@ export const withSentry = (origHandler: NextApiHandler): WrappedNextApiHandler =
           // If there is a trace header set, extract the data from it (parentSpanId, traceId, and sampling decision)
           let traceparentData;
           if (req.headers && isString(req.headers['sentry-trace'])) {
-            traceparentData = extractTraceparentData(req.headers['sentry-trace'] as string);
+            traceparentData = extractTraceparentData(req.headers['sentry-trace']);
             logger.log(`[Tracing] Continuing trace ${traceparentData?.traceId}.`);
           }
 
diff --git a/packages/node/src/backend.ts b/packages/node/src/backend.ts
index 8220d690ceb4..fea0407b412b 100644
--- a/packages/node/src/backend.ts
+++ b/packages/node/src/backend.ts
@@ -41,7 +41,7 @@ export class NodeBackend extends BaseBackend<NodeOptions> {
         const message = `Non-Error exception captured with keys: ${extractExceptionKeysForMessage(exception)}`;
 
         getCurrentHub().configureScope(scope => {
-          scope.setExtra('__serialized__', normalizeToSize(exception as Record<string, unknown>));
+          scope.setExtra('__serialized__', normalizeToSize(exception));
         });
 
         ex = (hint && hint.syntheticException) || new Error(message);
diff --git a/packages/node/src/handlers.ts b/packages/node/src/handlers.ts
index c8156896acc8..0aa67d34267a 100644
--- a/packages/node/src/handlers.ts
+++ b/packages/node/src/handlers.ts
@@ -56,7 +56,7 @@ export function tracingHandler(): (
     // If there is a trace header set, we extract the data from it (parentSpanId, traceId, and sampling decision)
     let traceparentData;
     if (req.headers && isString(req.headers['sentry-trace'])) {
-      traceparentData = extractTraceparentData(req.headers['sentry-trace'] as string);
+      traceparentData = extractTraceparentData(req.headers['sentry-trace']);
     }
 
     const transaction = startTransaction(
diff --git a/packages/serverless/src/awslambda.ts b/packages/serverless/src/awslambda.ts
index c2f3bed8f333..7b9f6608332f 100644
--- a/packages/serverless/src/awslambda.ts
+++ b/packages/serverless/src/awslambda.ts
@@ -256,7 +256,7 @@ export function wrapHandler<TEvent, TResult>(
     let traceparentData;
     const eventWithHeaders = event as { headers?: { [key: string]: string } };
     if (eventWithHeaders.headers && isString(eventWithHeaders.headers['sentry-trace'])) {
-      traceparentData = extractTraceparentData(eventWithHeaders.headers['sentry-trace'] as string);
+      traceparentData = extractTraceparentData(eventWithHeaders.headers['sentry-trace']);
     }
     const transaction = startTransaction({
       name: context.functionName,
diff --git a/packages/serverless/src/gcpfunction/http.ts b/packages/serverless/src/gcpfunction/http.ts
index d9996842b18c..30f22187ac25 100644
--- a/packages/serverless/src/gcpfunction/http.ts
+++ b/packages/serverless/src/gcpfunction/http.ts
@@ -53,7 +53,7 @@ function _wrapHttpFunction(fn: HttpFunction, wrapOptions: Partial<HttpFunctionWr
     let traceparentData;
     const reqWithHeaders = req as { headers?: { [key: string]: string } };
     if (reqWithHeaders.headers && isString(reqWithHeaders.headers['sentry-trace'])) {
-      traceparentData = extractTraceparentData(reqWithHeaders.headers['sentry-trace'] as string);
+      traceparentData = extractTraceparentData(reqWithHeaders.headers['sentry-trace']);
     }
     const transaction = startTransaction({
       name: `${reqMethod} ${reqUrl}`,
diff --git a/packages/tracing/src/browser/request.ts b/packages/tracing/src/browser/request.ts
index 885d381017dc..76d19b054838 100644
--- a/packages/tracing/src/browser/request.ts
+++ b/packages/tracing/src/browser/request.ts
@@ -185,7 +185,7 @@ export function fetchCallback(
     const options = (handlerData.args[1] = (handlerData.args[1] as { [key: string]: any }) || {});
     let headers = options.headers;
     if (isInstanceOf(request, Request)) {
-      headers = (request as Request).headers;
+      headers = request.headers;
     }
     if (headers) {
       // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
diff --git a/packages/tracing/src/transaction.ts b/packages/tracing/src/transaction.ts
index 3b98a533f289..ca76fb635154 100644
--- a/packages/tracing/src/transaction.ts
+++ b/packages/tracing/src/transaction.ts
@@ -37,7 +37,7 @@ export class Transaction extends SpanClass implements TransactionInterface {
     super(transactionContext);
 
     if (isInstanceOf(hub, Hub)) {
-      this._hub = hub as Hub;
+      this._hub = hub;
     }
 
     this.name = transactionContext.name || '';
diff --git a/packages/utils/src/is.ts b/packages/utils/src/is.ts
index 08b90c1cf748..755a429d2b6b 100644
--- a/packages/utils/src/is.ts
+++ b/packages/utils/src/is.ts
@@ -9,7 +9,7 @@ import { Primitive } from '@sentry/types';
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isError(wat: any): boolean {
+export function isError(wat: any): wat is Error {
   switch (Object.prototype.toString.call(wat)) {
     case '[object Error]':
       return true;
@@ -29,7 +29,7 @@ export function isError(wat: any): boolean {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isErrorEvent(wat: any): boolean {
+export function isErrorEvent(wat: any): wat is ErrorEvent {
   return Object.prototype.toString.call(wat) === '[object ErrorEvent]';
 }
 
@@ -40,7 +40,7 @@ export function isErrorEvent(wat: any): boolean {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isDOMError(wat: any): boolean {
+export function isDOMError(wat: any): wat is DOMError {
   return Object.prototype.toString.call(wat) === '[object DOMError]';
 }
 
@@ -51,18 +51,18 @@ export function isDOMError(wat: any): boolean {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isDOMException(wat: any): boolean {
+export function isDOMException(wat: any): wat is DOMException {
   return Object.prototype.toString.call(wat) === '[object DOMException]';
 }
 
 /**
- * Checks whether given value's type is a string
+ * Checks whether the given value's type is string
  * {@link isString}.
  *
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isString(wat: any): boolean {
+export function isString(wat: any): wat is string {
   return Object.prototype.toString.call(wat) === '[object String]';
 }
 
@@ -84,7 +84,7 @@ export function isPrimitive(wat: any): wat is Primitive {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isPlainObject(wat: any): boolean {
+export function isPlainObject(wat: any): wat is { [key: string]: unknown } {
   return Object.prototype.toString.call(wat) === '[object Object]';
 }
 
@@ -95,7 +95,7 @@ export function isPlainObject(wat: any): boolean {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isEvent(wat: any): boolean {
+export function isEvent(wat: any): wat is Event {
   return typeof Event !== 'undefined' && isInstanceOf(wat, Event);
 }
 
@@ -106,7 +106,7 @@ export function isEvent(wat: any): boolean {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isElement(wat: any): boolean {
+export function isElement(wat: any): wat is Element {
   return typeof Element !== 'undefined' && isInstanceOf(wat, Element);
 }
 
@@ -117,7 +117,7 @@ export function isElement(wat: any): boolean {
  * @param wat A value to be checked.
  * @returns A boolean representing the result.
  */
-export function isRegExp(wat: any): boolean {
+export function isRegExp(wat: any): wat is RegExp {
   return Object.prototype.toString.call(wat) === '[object RegExp]';
 }
 
@@ -140,6 +140,12 @@ export function isThenable(wat: any): boolean {
 export function isSyntheticEvent(wat: any): boolean {
   return isPlainObject(wat) && 'nativeEvent' in wat && 'preventDefault' in wat && 'stopPropagation' in wat;
 }
+
+// Having the two different types is necessary because some types packages type classes as functions (in addition to
+// being objects with a `new` method), and some only type them as `new`-able objects
+type Constructor<T> = (...args: any[]) => T;
+type ClassWithConstructor<T> = { new (...args: any[]): T };
+
 /**
  * Checks whether given value's type is an instance of provided constructor.
  * {@link isInstanceOf}.
@@ -148,7 +154,7 @@ export function isSyntheticEvent(wat: any): boolean {
  * @param base A constructor to be used in a check.
  * @returns A boolean representing the result.
  */
-export function isInstanceOf(wat: any, base: any): boolean {
+export function isInstanceOf<T>(wat: any, base: Constructor<T> | ClassWithConstructor<T>): wat is T {
   try {
     return wat instanceof base;
   } catch (_e) {
diff --git a/packages/utils/src/object.ts b/packages/utils/src/object.ts
index b44575ca92cd..1e51eaa5a87c 100644
--- a/packages/utils/src/object.ts
+++ b/packages/utils/src/object.ts
@@ -103,7 +103,7 @@ function getWalkSource(
       currentTarget?: unknown;
     }
 
-    const event = value as SimpleEvent;
+    const event = (value as unknown) as SimpleEvent;
 
     const source: {
       [key: string]: any;
@@ -381,9 +381,8 @@ export function extractExceptionKeysForMessage(exception: any, maxLength: number
  * Given any object, return the new object with removed keys that value was `undefined`.
  * Works recursively on objects and arrays.
  */
-export function dropUndefinedKeys<T>(val: T): T {
-  if (isPlainObject(val)) {
-    const obj = val as { [key: string]: any };
+export function dropUndefinedKeys<T>(obj: T): T {
+  if (isPlainObject(obj)) {
     const rv: { [key: string]: any } = {};
     for (const key of Object.keys(obj)) {
       if (typeof obj[key] !== 'undefined') {
@@ -393,11 +392,11 @@ export function dropUndefinedKeys<T>(val: T): T {
     return rv as T;
   }
 
-  if (Array.isArray(val)) {
-    return (val as any[]).map(dropUndefinedKeys) as any;
+  if (Array.isArray(obj)) {
+    return (obj as any[]).map(dropUndefinedKeys) as any;
   }
 
-  return val;
+  return obj;
 }
 
 /**