diff --git a/packages/nextjs/src/config/webpackPluginOptions.ts b/packages/nextjs/src/config/webpackPluginOptions.ts
index 1bca9bff49b6..7b183047896a 100644
--- a/packages/nextjs/src/config/webpackPluginOptions.ts
+++ b/packages/nextjs/src/config/webpackPluginOptions.ts
@@ -11,37 +11,43 @@ export function getWebpackPluginOptions(
   buildContext: BuildContext,
   sentryBuildOptions: SentryBuildOptions,
 ): SentryWebpackPluginOptions {
-  const { buildId, isServer, config: userNextConfig, dir: projectDir, nextRuntime } = buildContext;
+  const { buildId, isServer, config: userNextConfig, dir, nextRuntime } = buildContext;
 
   const prefixInsert = !isServer ? 'Client' : nextRuntime === 'edge' ? 'Edge' : 'Node.js';
 
-  const distDirAbsPath = path.join(projectDir, (userNextConfig as NextConfigObject).distDir || '.next'); // `.next` is the default directory
+  // We need to convert paths to posix because Glob patterns use `\` to escape
+  // glob characters. This clashes with Windows path separators.
+  // See: https://www.npmjs.com/package/glob
+  const projectDir = dir.replace(/\\/g, '/');
+  // `.next` is the default directory
+  const distDir = (userNextConfig as NextConfigObject).distDir?.replace(/\\/g, '/') ?? '.next';
+  const distDirAbsPath = path.posix.join(projectDir, distDir);
 
   let sourcemapUploadAssets: string[] = [];
   const sourcemapUploadIgnore: string[] = [];
 
   if (isServer) {
     sourcemapUploadAssets.push(
-      path.join(distDirAbsPath, 'server', '**'), // This is normally where Next.js outputs things
-      path.join(distDirAbsPath, 'serverless', '**'), // This was the output location for serverless Next.js
+      path.posix.join(distDirAbsPath, 'server', '**'), // This is normally where Next.js outputs things
+      path.posix.join(distDirAbsPath, 'serverless', '**'), // This was the output location for serverless Next.js
     );
   } else {
     if (sentryBuildOptions.widenClientFileUpload) {
-      sourcemapUploadAssets.push(path.join(distDirAbsPath, 'static', 'chunks', '**'));
+      sourcemapUploadAssets.push(path.posix.join(distDirAbsPath, 'static', 'chunks', '**'));
     } else {
       sourcemapUploadAssets.push(
-        path.join(distDirAbsPath, 'static', 'chunks', 'pages', '**'),
-        path.join(distDirAbsPath, 'static', 'chunks', 'app', '**'),
+        path.posix.join(distDirAbsPath, 'static', 'chunks', 'pages', '**'),
+        path.posix.join(distDirAbsPath, 'static', 'chunks', 'app', '**'),
       );
     }
 
     // TODO: We should think about uploading these when `widenClientFileUpload` is `true`. They may be useful in some situations.
     sourcemapUploadIgnore.push(
-      path.join(distDirAbsPath, 'static', 'chunks', 'framework-*'),
-      path.join(distDirAbsPath, 'static', 'chunks', 'framework.*'),
-      path.join(distDirAbsPath, 'static', 'chunks', 'main-*'),
-      path.join(distDirAbsPath, 'static', 'chunks', 'polyfills-*'),
-      path.join(distDirAbsPath, 'static', 'chunks', 'webpack-*'),
+      path.posix.join(distDirAbsPath, 'static', 'chunks', 'framework-*'),
+      path.posix.join(distDirAbsPath, 'static', 'chunks', 'framework.*'),
+      path.posix.join(distDirAbsPath, 'static', 'chunks', 'main-*'),
+      path.posix.join(distDirAbsPath, 'static', 'chunks', 'polyfills-*'),
+      path.posix.join(distDirAbsPath, 'static', 'chunks', 'webpack-*'),
     );
   }
 
@@ -79,9 +85,9 @@ export function getWebpackPluginOptions(
             // We only care to delete client bundle source maps because they would be the ones being served.
             // Removing the server source maps crashes Vercel builds for (thus far) unknown reasons:
             // https://github.com/getsentry/sentry-javascript/issues/13099
-            path.join(distDirAbsPath, 'static', '**', '*.js.map'),
-            path.join(distDirAbsPath, 'static', '**', '*.mjs.map'),
-            path.join(distDirAbsPath, 'static', '**', '*.cjs.map'),
+            path.posix.join(distDirAbsPath, 'static', '**', '*.js.map'),
+            path.posix.join(distDirAbsPath, 'static', '**', '*.mjs.map'),
+            path.posix.join(distDirAbsPath, 'static', '**', '*.cjs.map'),
           ]
         : undefined,
       ...sentryBuildOptions.unstable_sentryWebpackPluginOptions?.sourcemaps,
diff --git a/packages/nextjs/test/config/webpack/webpackPluginOptions.test.ts b/packages/nextjs/test/config/webpack/webpackPluginOptions.test.ts
index 557859b2a7e1..177077d2b5c4 100644
--- a/packages/nextjs/test/config/webpack/webpackPluginOptions.test.ts
+++ b/packages/nextjs/test/config/webpack/webpackPluginOptions.test.ts
@@ -2,6 +2,7 @@ import type { BuildContext, NextConfigObject } from '../../../src/config/types';
 import { getWebpackPluginOptions } from '../../../src/config/webpackPluginOptions';
 
 function generateBuildContext(overrides: {
+  dir?: string;
   isServer: boolean;
   nextjsConfig?: NextConfigObject;
 }): BuildContext {
@@ -9,7 +10,7 @@ function generateBuildContext(overrides: {
     dev: false, // The plugin is not included in dev mode
     isServer: overrides.isServer,
     buildId: 'test-build-id',
-    dir: '/my/project/dir',
+    dir: overrides.dir ?? '/my/project/dir',
     config: overrides.nextjsConfig ?? {},
     totalPages: 2,
     defaultLoaders: true,
@@ -171,4 +172,23 @@ describe('getWebpackPluginOptions()', () => {
       assets: [],
     });
   });
+
+  it('passes posix paths to the plugin', () => {
+    const buildContext = generateBuildContext({
+      dir: 'C:\\my\\windows\\project\\dir',
+      nextjsConfig: { distDir: '.dist\\v1' },
+      isServer: false,
+    });
+    const generatedPluginOptions = getWebpackPluginOptions(buildContext, { widenClientFileUpload: true });
+    expect(generatedPluginOptions.sourcemaps).toMatchObject({
+      assets: ['C:/my/windows/project/dir/.dist/v1/static/chunks/**'],
+      ignore: [
+        'C:/my/windows/project/dir/.dist/v1/static/chunks/framework-*',
+        'C:/my/windows/project/dir/.dist/v1/static/chunks/framework.*',
+        'C:/my/windows/project/dir/.dist/v1/static/chunks/main-*',
+        'C:/my/windows/project/dir/.dist/v1/static/chunks/polyfills-*',
+        'C:/my/windows/project/dir/.dist/v1/static/chunks/webpack-*',
+      ],
+    });
+  });
 });