diff --git a/.changeset/complexselector-above-placement-gap.md b/.changeset/complexselector-above-placement-gap.md
new file mode 100644
index 000000000000..19ba0973aa45
--- /dev/null
+++ b/.changeset/complexselector-above-placement-gap.md
@@ -0,0 +1,7 @@
+---
+'@astryxdesign/core': patch
+---
+
+[fix] ComplexSelector: the popup keeps its clearance when opening upward (`placement="above"`). The popup layer only set the gap on its block-start edge, which spaces a downward-opening popup but left an upward-opening one flush against the trigger. Both block edges now carry the gap, matching Popover.
+
+@AKnassa
diff --git a/packages/core/src/ComplexSelector/ComplexSelector.test.tsx b/packages/core/src/ComplexSelector/ComplexSelector.test.tsx
index 7e0cd6200343..c9fbb889a1fa 100644
--- a/packages/core/src/ComplexSelector/ComplexSelector.test.tsx
+++ b/packages/core/src/ComplexSelector/ComplexSelector.test.tsx
@@ -12,8 +12,24 @@
 import {describe, expect, it, vi} from 'vitest';
 import {render, screen, waitFor} from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
+import * as stylex from '@stylexjs/stylex';
+import {spacingVars} from '../theme/tokens.stylex';
 import {ComplexSelector} from './ComplexSelector';
 
+// StyleX emits one deterministic atomic class per property/value pair, so an
+// element carries a probe's class exactly when it has the same declaration.
+// The dev-mode debug class (contains "__") varies by source location and is
+// excluded from the comparison.
+const probe = stylex.create({
+  blockStartGap: {marginBlockStart: spacingVars['--spacing-1']},
+  blockEndGap: {marginBlockEnd: spacingVars['--spacing-1']},
+});
+
+function atomicClasses(style: (typeof probe)[keyof typeof probe]): string[] {
+  const {className = ''} = stylex.props(style);
+  return className.split(' ').filter(c => c !== '' && !c.includes('__'));
+}
+
 type FruitValue = {
   fruit: 'Apple' | 'Banana';
   ripeness: 'Crisp' | 'Ripe' | 'Juicy';
@@ -153,4 +169,33 @@ describe('ComplexSelector', () => {
     await user.click(screen.getByRole('button', {name: 'Done', ...h}));
     expect(trigger).toHaveAttribute('aria-expanded', 'false');
   });
+
+  it('keeps the popup gap on both block edges so placement="above" clears the trigger', async () => {
+    // #4803: the popup layer only set marginBlockStart, which spaces a popup
+    // opening downward but leaves an upward-opening one flush against the
+    // trigger. Both block edges must carry the gap, mirroring Popover's `gap`
+    // style, so the clearance holds whichever way the layer opens.
+    const user = userEvent.setup();
+    render(
+      <ComplexSelector
+        label="Fruit blend"
+        value="Apple"
+        triggerLabel="Apple"
+        placement="above">
+        {() => <div>Surface</div>}
+      </ComplexSelector>,
+    );
+    await user.click(screen.getByRole('button', {name: 'Fruit blend'}));
+
+    const layer = document.querySelector('[popover]');
+    expect(layer).not.toBeNull();
+    const startGapClasses = atomicClasses(probe.blockStartGap);
+    const endGapClasses = atomicClasses(probe.blockEndGap);
+    // Guard against a vacuous pass if the probe ever compiles to no classes.
+    expect(startGapClasses.length).toBeGreaterThan(0);
+    expect(endGapClasses.length).toBeGreaterThan(0);
+    for (const cls of [...startGapClasses, ...endGapClasses]) {
+      expect(layer!.classList.contains(cls)).toBe(true);
+    }
+  });
 });
diff --git a/packages/core/src/ComplexSelector/ComplexSelector.tsx b/packages/core/src/ComplexSelector/ComplexSelector.tsx
index d165b5feac6a..528e7f78619d 100644
--- a/packages/core/src/ComplexSelector/ComplexSelector.tsx
+++ b/packages/core/src/ComplexSelector/ComplexSelector.tsx
@@ -115,7 +115,10 @@ const styles = stylex.create({
   },
   popover: {
     minWidth: 'anchor-size(width)',
+    // Both block edges carry the gap so the popup keeps its clearance
+    // whichever way it opens (placement="above" spaces via the end edge).
     marginBlockStart: spacingVars['--spacing-1'],
+    marginBlockEnd: spacingVars['--spacing-1'],
   },
   content: {
     boxSizing: 'border-box',