diff --git a/.size-limit.js b/.size-limit.js
index 61fb027289d3..dc8e4f9df560 100644
--- a/.size-limit.js
+++ b/.size-limit.js
@@ -120,7 +120,7 @@ module.exports = [
     import: createImport('init', 'ErrorBoundary', 'reactRouterV6BrowserTracingIntegration'),
     ignore: ['react/jsx-runtime'],
     gzip: true,
-    limit: '41 KB',
+    limit: '42 KB',
   },
   // Vue SDK (ESM)
   {
diff --git a/packages/core/src/tracing/trace.ts b/packages/core/src/tracing/trace.ts
index 7a2229090e97..bbb956acf042 100644
--- a/packages/core/src/tracing/trace.ts
+++ b/packages/core/src/tracing/trace.ts
@@ -58,7 +58,7 @@ export function startSpan<T>(options: StartSpanOptions, callback: (span: Span) =
 
     return wrapper(() => {
       const scope = getCurrentScope();
-      const parentSpan = getParentSpan(scope);
+      const parentSpan = getParentSpan(scope, customParentSpan);
 
       const shouldSkipSpan = options.onlyIfParent && !parentSpan;
       const activeSpan = shouldSkipSpan
@@ -116,7 +116,7 @@ export function startSpanManual<T>(options: StartSpanOptions, callback: (span: S
 
     return wrapper(() => {
       const scope = getCurrentScope();
-      const parentSpan = getParentSpan(scope);
+      const parentSpan = getParentSpan(scope, customParentSpan);
 
       const shouldSkipSpan = options.onlyIfParent && !parentSpan;
       const activeSpan = shouldSkipSpan
@@ -176,7 +176,7 @@ export function startInactiveSpan(options: StartSpanOptions): Span {
 
   return wrapper(() => {
     const scope = getCurrentScope();
-    const parentSpan = getParentSpan(scope);
+    const parentSpan = getParentSpan(scope, customParentSpan);
 
     const shouldSkipSpan = options.onlyIfParent && !parentSpan;
 
@@ -489,7 +489,17 @@ function _startChildSpan(parentSpan: Span, scope: Scope, spanArguments: SentrySp
   return childSpan;
 }
 
-function getParentSpan(scope: Scope): SentrySpan | undefined {
+function getParentSpan(scope: Scope, customParentSpan: Span | null | undefined): SentrySpan | undefined {
+  // always use the passed in span directly
+  if (customParentSpan) {
+    return customParentSpan as SentrySpan;
+  }
+
+  // This is different from `undefined` as it means the user explicitly wants no parent span
+  if (customParentSpan === null) {
+    return undefined;
+  }
+
   const span = _getSpanForScope(scope) as SentrySpan | undefined;
 
   if (!span) {
diff --git a/packages/core/test/lib/tracing/trace.test.ts b/packages/core/test/lib/tracing/trace.test.ts
index 6d25afe13d3e..eccbb57f1610 100644
--- a/packages/core/test/lib/tracing/trace.test.ts
+++ b/packages/core/test/lib/tracing/trace.test.ts
@@ -620,6 +620,44 @@ describe('startSpan', () => {
         });
       });
     });
+
+    it('explicit parentSpan takes precedence over parentSpanIsAlwaysRootSpan=true', () => {
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 1,
+        parentSpanIsAlwaysRootSpan: true,
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+
+      const parentSpan = startInactiveSpan({ name: 'parent span' });
+
+      startSpan({ name: 'parent span' }, () => {
+        startSpan({ name: 'child span' }, () => {
+          startSpan({ name: 'grand child span', parentSpan }, grandChildSpan => {
+            expect(spanToJSON(grandChildSpan).parent_span_id).toBe(parentSpan.spanContext().spanId);
+          });
+        });
+      });
+    });
+
+    it('explicit parentSpan=null takes precedence over parentSpanIsAlwaysRootSpan=true', () => {
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 1,
+        parentSpanIsAlwaysRootSpan: true,
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+
+      startSpan({ name: 'parent span' }, () => {
+        startSpan({ name: 'child span' }, () => {
+          startSpan({ name: 'grand child span', parentSpan: null }, grandChildSpan => {
+            expect(spanToJSON(grandChildSpan).parent_span_id).toBe(undefined);
+          });
+        });
+      });
+    });
   });
 
   it('samples with a tracesSampler', () => {
@@ -1174,6 +1212,46 @@ describe('startSpanManual', () => {
         span.end();
       });
     });
+
+    it('explicit parentSpan takes precedence over parentSpanIsAlwaysRootSpan=true', () => {
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 1,
+        parentSpanIsAlwaysRootSpan: true,
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+
+      const parentSpan = startInactiveSpan({ name: 'parent span' });
+
+      startSpan({ name: 'parent span' }, () => {
+        startSpan({ name: 'child span' }, () => {
+          startSpanManual({ name: 'grand child span', parentSpan }, grandChildSpan => {
+            expect(spanToJSON(grandChildSpan).parent_span_id).toBe(parentSpan.spanContext().spanId);
+            grandChildSpan.end();
+          });
+        });
+      });
+    });
+
+    it('explicit parentSpan=null takes precedence over parentSpanIsAlwaysRootSpan=true', () => {
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 1,
+        parentSpanIsAlwaysRootSpan: true,
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+
+      startSpan({ name: 'parent span' }, () => {
+        startSpan({ name: 'child span' }, () => {
+          startSpanManual({ name: 'grand child span', parentSpan: null }, grandChildSpan => {
+            expect(spanToJSON(grandChildSpan).parent_span_id).toBe(undefined);
+            grandChildSpan.end();
+          });
+        });
+      });
+    });
   });
 
   it('sets a child span reference on the parent span', () => {
@@ -1543,6 +1621,44 @@ describe('startInactiveSpan', () => {
         });
       });
     });
+
+    it('explicit parentSpan takes precedence over parentSpanIsAlwaysRootSpan=true', () => {
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 1,
+        parentSpanIsAlwaysRootSpan: true,
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+
+      const parentSpan = startInactiveSpan({ name: 'parent span' });
+
+      startSpan({ name: 'parent span' }, () => {
+        startSpan({ name: 'child span' }, () => {
+          const grandChildSpan = startInactiveSpan({ name: 'grand child span', parentSpan });
+          expect(spanToJSON(grandChildSpan).parent_span_id).toBe(parentSpan.spanContext().spanId);
+          grandChildSpan.end();
+        });
+      });
+    });
+
+    it('explicit parentSpan=null takes precedence over parentSpanIsAlwaysRootSpan=true', () => {
+      const options = getDefaultTestClientOptions({
+        tracesSampleRate: 1,
+        parentSpanIsAlwaysRootSpan: true,
+      });
+      client = new TestClient(options);
+      setCurrentClient(client);
+      client.init();
+
+      startSpan({ name: 'parent span' }, () => {
+        startSpan({ name: 'child span' }, () => {
+          const grandChildSpan = startInactiveSpan({ name: 'grand child span', parentSpan: null });
+          expect(spanToJSON(grandChildSpan).parent_span_id).toBe(undefined);
+          grandChildSpan.end();
+        });
+      });
+    });
   });
 
   it('includes the scope at the time the span was started when finished', async () => {