diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5db35c9156..d703589db5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@
 
 ## Unreleased
 
+### Fixes
+
+- Resolve relative `SOURCEMAP_FILE` paths against the project root in the Xcode build script ([#5730](https://github.com/getsentry/sentry-react-native/pull/5730))
+
 ### Dependencies
 
 - Bump JavaScript SDK from v10.39.0 to v10.40.0 ([#5715](https://github.com/getsentry/sentry-react-native/pull/5715))
diff --git a/packages/core/scripts/sentry-xcode.sh b/packages/core/scripts/sentry-xcode.sh
index 2ab36fc1b1..973f358b39 100755
--- a/packages/core/scripts/sentry-xcode.sh
+++ b/packages/core/scripts/sentry-xcode.sh
@@ -15,6 +15,13 @@ RN_PROJECT_ROOT="${PROJECT_DIR}/.."
 [ -z "$SENTRY_PROPERTIES" ] && export SENTRY_PROPERTIES=sentry.properties
 [ -z "$SENTRY_DOTENV_PATH" ] && [ -f "$RN_PROJECT_ROOT/.env.sentry-build-plugin" ] && export SENTRY_DOTENV_PATH="$RN_PROJECT_ROOT/.env.sentry-build-plugin"
 [ -z "$SOURCEMAP_FILE" ] && export SOURCEMAP_FILE="$DERIVED_FILE_DIR/main.jsbundle.map"
+# Resolve relative SOURCEMAP_FILE to absolute. The script runs from `ios/` (Xcode's PWD),
+# but users typically specify paths relative to the project root. Without this, sentry-cli
+# would resolve relative paths against `ios/` and fail to find the file.
+# See: https://github.com/getsentry/sentry-react-native/issues/3889
+if [[ "$SOURCEMAP_FILE" != /* ]]; then
+  export SOURCEMAP_FILE="$(cd "$RN_PROJECT_ROOT" && pwd)/$SOURCEMAP_FILE"
+fi
 
 if [ -z "$SENTRY_CLI_EXECUTABLE" ]; then
   # Try standard resolution safely
diff --git a/packages/core/test/scripts/sentry-xcode-scripts.test.ts b/packages/core/test/scripts/sentry-xcode-scripts.test.ts
index aac5d69566..7e9252ad05 100644
--- a/packages/core/test/scripts/sentry-xcode-scripts.test.ts
+++ b/packages/core/test/scripts/sentry-xcode-scripts.test.ts
@@ -454,4 +454,81 @@ describe('sentry-xcode.sh', () => {
     expect(result.stdout).toContain('SENTRY_DISABLE_AUTO_UPLOAD=true');
     expect(result.stdout).toContain('skipping sourcemaps upload');
   });
+
+  describe('SOURCEMAP_FILE path resolution', () => {
+    // Returns a mock sentry-cli that prints the SOURCEMAP_FILE env var it received.
+    const makeSourcmapEchoScript = (dir: string): string => {
+      const scriptPath = path.join(dir, 'mock-sentry-cli-echo-sourcemap.js');
+      fs.writeFileSync(
+        scriptPath,
+        `
+        const sourcemapFile = process.env.SOURCEMAP_FILE || 'not-set';
+        console.log('SOURCEMAP_FILE=' + sourcemapFile);
+        process.exit(0);
+        `,
+      );
+      return scriptPath;
+    };
+
+    it('leaves an absolute SOURCEMAP_FILE unchanged', () => {
+      const absolutePath = path.join(tempDir, 'absolute', 'main.jsbundle.map');
+      const echoScript = makeSourcmapEchoScript(tempDir);
+
+      const result = runScript({
+        SENTRY_CLI_EXECUTABLE: echoScript,
+        SOURCEMAP_FILE: absolutePath,
+      });
+
+      expect(result.exitCode).toBe(0);
+      expect(result.stdout).toContain(`SOURCEMAP_FILE=${absolutePath}`);
+    });
+
+    it('resolves a relative SOURCEMAP_FILE against the project root, not ios/', () => {
+      // PROJECT_DIR is tempDir (simulates the ios/ folder).
+      // RN_PROJECT_ROOT = PROJECT_DIR/.. = parent of tempDir.
+      // A user setting SOURCEMAP_FILE=relative/path.map expects it relative to the project root.
+      const echoScript = makeSourcmapEchoScript(tempDir);
+
+      const result = runScript({
+        SENTRY_CLI_EXECUTABLE: echoScript,
+        SOURCEMAP_FILE: 'relative/path.map',
+      });
+
+      const projectRoot = path.dirname(tempDir); // PROJECT_DIR/.. = RN_PROJECT_ROOT
+      const expectedPath = path.join(projectRoot, 'relative/path.map');
+
+      expect(result.exitCode).toBe(0);
+      expect(result.stdout).toContain(`SOURCEMAP_FILE=${expectedPath}`);
+    });
+
+    it('resolves a ./prefixed SOURCEMAP_FILE against the project root', () => {
+      const echoScript = makeSourcmapEchoScript(tempDir);
+
+      const result = runScript({
+        SENTRY_CLI_EXECUTABLE: echoScript,
+        SOURCEMAP_FILE: './maps/main.jsbundle.map',
+      });
+
+      // The script concatenates: "$(cd RN_PROJECT_ROOT && pwd)/./maps/main.jsbundle.map"
+      // The ./ is preserved but the path is absolute and valid for sentry-cli.
+      const projectRoot = path.dirname(tempDir);
+      const expectedPath = `${projectRoot}/./maps/main.jsbundle.map`;
+
+      expect(result.exitCode).toBe(0);
+      expect(result.stdout).toContain(`SOURCEMAP_FILE=${expectedPath}`);
+    });
+
+    it('uses the absolute default SOURCEMAP_FILE when not set by the user', () => {
+      const echoScript = makeSourcmapEchoScript(tempDir);
+
+      const result = runScript({
+        SENTRY_CLI_EXECUTABLE: echoScript,
+        // SOURCEMAP_FILE intentionally not set — script should default to $DERIVED_FILE_DIR/main.jsbundle.map
+        DERIVED_FILE_DIR: tempDir,
+      });
+
+      expect(result.exitCode).toBe(0);
+      expect(result.stdout).toContain(`SOURCEMAP_FILE=${tempDir}/main.jsbundle.map`);
+    });
+  });
 });