diff --git a/backend/src/api/public/v1/members/work-experiences/updateMemberWorkExperience.ts b/backend/src/api/public/v1/members/work-experiences/updateMemberWorkExperience.ts
index 62ce2277f0..f0ee3462e5 100644
--- a/backend/src/api/public/v1/members/work-experiences/updateMemberWorkExperience.ts
+++ b/backend/src/api/public/v1/members/work-experiences/updateMemberWorkExperience.ts
@@ -2,27 +2,50 @@ import type { Request, Response } from 'express'
 import { z } from 'zod'
 
 import { captureApiChange, memberEditOrganizationsAction } from '@crowd/audit-logs'
-import { BadRequestError, NotFoundError, sanitizeMemberOrganizationDateRange } from '@crowd/common'
-import { signalMemberUpdate } from '@crowd/common_services'
+import {
+  BadRequestError,
+  ConflictError,
+  NotFoundError,
+  sanitizeMemberOrganizationDateRange,
+} from '@crowd/common'
+import { normalizeMemberOrganizationDate, signalMemberUpdate } from '@crowd/common_services'
 import {
   MemberField,
   cleanSoftDeletedMemberOrganization,
+  deleteMemberOrganizations,
   fetchManyMemberOrgsWithOrgData,
   fetchMemberOrganizations,
   findMemberById,
   optionsQx,
   updateMemberOrganization,
 } from '@crowd/data-access-layer'
-import type { MemberOrganizationDateRange, MemberOrganizationUpdate } from '@crowd/types'
+import type {
+  IMemberOrganization,
+  MemberOrganizationDateRange,
+  MemberOrganizationUpdate,
+} from '@crowd/types'
 
 import { ok } from '@/utils/api'
 import {
   getOverlappingGroupedMemberOrganizations,
   groupMemberOrganizations,
+  isCollapsibleMemberOrganization,
   toMemberWorkExperience,
 } from '@/utils/mapper'
 import { validateOrThrow } from '@/utils/validation'
 
+/** Matches the active unique index on memberOrganizations (org + date range). */
+function sameUniqueKey(
+  a: Pick<IMemberOrganization, 'organizationId' | 'dateStart' | 'dateEnd'>,
+  b: Pick<IMemberOrganization, 'organizationId' | 'dateStart' | 'dateEnd'>,
+): boolean {
+  return (
+    a.organizationId === b.organizationId &&
+    normalizeMemberOrganizationDate(a.dateStart) === normalizeMemberOrganizationDate(b.dateStart) &&
+    normalizeMemberOrganizationDate(a.dateEnd) === normalizeMemberOrganizationDate(b.dateEnd)
+  )
+}
+
 const paramsSchema = z.object({
   memberId: z.uuid(),
   workExperienceId: z.uuid(),
@@ -83,13 +106,51 @@ export async function updateMemberWorkExperience(req: Request, res: Response): P
       captureOldState(existing)
 
       await qx.tx(async (tx) => {
+        // Avoid unique-index collisions before we UPDATE the visible row.
+        const conflictingRows = memberOrgs.filter(
+          (row) =>
+            !!row.id &&
+            row.id !== workExperienceId &&
+            sameUniqueKey(row, {
+              organizationId: data.organizationId,
+              dateStart: dates.dateStart,
+              dateEnd: dates.dateEnd,
+            }),
+        )
+
+        // Conflict if a visible work experience with the same dates already exists. Throw a conflict error.
+        const conflictingVisibleIds = conflictingRows
+          .filter((row) => !isCollapsibleMemberOrganization(row))
+          .map((row) => row.id)
+          .filter((id): id is string => !!id)
+
+        if (conflictingVisibleIds.length > 0) {
+          throw new ConflictError('A work experience with the same dates already exists')
+        }
+
+        // Conflict if a collapsible work experience with the same dates already exists.
+        // Soft-delete it so the visible update can take that unique key.
+        const conflictingHiddenIds = conflictingRows
+          .filter((row) => isCollapsibleMemberOrganization(row))
+          .map((row) => row.id)
+          .filter((id): id is string => !!id)
+
+        if (conflictingHiddenIds.length > 0) {
+          await deleteMemberOrganizations(tx, memberId, conflictingHiddenIds)
+        }
+
+        // Fan-out below should not touch rows we just soft-deleted.
+        const memberOrgsAfterConflict = memberOrgs.filter(
+          (row) => !row.id || !conflictingHiddenIds.includes(row.id),
+        )
+
         await cleanSoftDeletedMemberOrganization(tx, memberId, data.organizationId, update)
         await updateMemberOrganization(tx, memberId, workExperienceId, update)
 
         const overlapBasis = { ...existing, ...update }
 
         const overlappingGroupedRows = getOverlappingGroupedMemberOrganizations(
-          memberOrgs,
+          memberOrgsAfterConflict,
           overlapBasis,
         )
 
diff --git a/backend/src/utils/mapper.ts b/backend/src/utils/mapper.ts
index d4f7e57c9a..d7b2e212c6 100644
--- a/backend/src/utils/mapper.ts
+++ b/backend/src/utils/mapper.ts
@@ -15,7 +15,7 @@ function memberOrganizationsOverlap<T extends IMemberOrganization>(a: T, b: T):
   )
 }
 
-function isCollapsibleMemberOrganization<T extends IMemberOrganization>(row: T): boolean {
+export function isCollapsibleMemberOrganization<T extends IMemberOrganization>(row: T): boolean {
   if (!row.source) {
     return false
   }