diff --git a/polkadot/node/core/approval-voting/src/approval_checking.rs b/polkadot/node/core/approval-voting/src/approval_checking.rs
index 3b7262a46826..c7f38619ea1f 100644
--- a/polkadot/node/core/approval-voting/src/approval_checking.rs
+++ b/polkadot/node/core/approval-voting/src/approval_checking.rs
@@ -712,13 +712,13 @@ mod tests {
 		}
 		.into();
 
-		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
-		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
+		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);
 
-		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1);
-		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1, false);
+		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1, false);
 
-		approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + 2);
+		approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + 2, false);
 
 		let approvals = bitvec![u8, BitOrderLsb0; 1; 5];
 
@@ -757,8 +757,10 @@ mod tests {
 		}
 		.into();
 
-		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
-		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, true);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, false);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, true);
 
 		let approvals = bitvec![u8, BitOrderLsb0; 0; 10];
 
@@ -798,10 +800,10 @@ mod tests {
 		}
 		.into();
 
-		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
-		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
+		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);
 
-		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, false);
 
 		let mut approvals = bitvec![u8, BitOrderLsb0; 0; 10];
 		approvals.set(0, true);
@@ -844,11 +846,11 @@ mod tests {
 		}
 		.into();
 
-		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
-		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
+		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);
 
-		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick);
-		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick, false);
+		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick, false);
 
 		let mut approvals = bitvec![u8, BitOrderLsb0; 0; n_validators];
 		approvals.set(0, true);
@@ -913,14 +915,24 @@ mod tests {
 		}
 		.into();
 
-		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
-		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
+		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);
 
-		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1);
-		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1, false);
+		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1, false);
 
-		approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + no_show_duration + 2);
-		approval_entry.import_assignment(2, ValidatorIndex(5), block_tick + no_show_duration + 2);
+		approval_entry.import_assignment(
+			2,
+			ValidatorIndex(4),
+			block_tick + no_show_duration + 2,
+			false,
+		);
+		approval_entry.import_assignment(
+			2,
+			ValidatorIndex(5),
+			block_tick + no_show_duration + 2,
+			false,
+		);
 
 		let mut approvals = bitvec![u8, BitOrderLsb0; 0; n_validators];
 		approvals.set(0, true);
@@ -1007,14 +1019,24 @@ mod tests {
 		}
 		.into();
 
-		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick);
-		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick);
+		approval_entry.import_assignment(0, ValidatorIndex(0), block_tick, false);
+		approval_entry.import_assignment(0, ValidatorIndex(1), block_tick, false);
 
-		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1);
-		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1);
+		approval_entry.import_assignment(1, ValidatorIndex(2), block_tick + 1, false);
+		approval_entry.import_assignment(1, ValidatorIndex(3), block_tick + 1, false);
 
-		approval_entry.import_assignment(2, ValidatorIndex(4), block_tick + no_show_duration + 2);
-		approval_entry.import_assignment(2, ValidatorIndex(5), block_tick + no_show_duration + 2);
+		approval_entry.import_assignment(
+			2,
+			ValidatorIndex(4),
+			block_tick + no_show_duration + 2,
+			false,
+		);
+		approval_entry.import_assignment(
+			2,
+			ValidatorIndex(5),
+			block_tick + no_show_duration + 2,
+			false,
+		);
 
 		let mut approvals = bitvec![u8, BitOrderLsb0; 0; n_validators];
 		approvals.set(0, true);
@@ -1066,7 +1088,7 @@ mod tests {
 			},
 		);
 
-		approval_entry.import_assignment(3, ValidatorIndex(6), block_tick);
+		approval_entry.import_assignment(3, ValidatorIndex(6), block_tick, false);
 		approvals.set(6, true);
 
 		let tranche_now = no_show_duration as DelayTranche + 3;
@@ -1176,7 +1198,7 @@ mod tests {
 			// Populate the requested tranches. The assignments aren't inspected in
 			// this test.
 			for &t in &test_tranche {
-				approval_entry.import_assignment(t, ValidatorIndex(0), 0)
+				approval_entry.import_assignment(t, ValidatorIndex(0), 0, false);
 			}
 
 			let filled_tranches = filled_tranche_iterator(approval_entry.tranches());
diff --git a/polkadot/node/core/approval-voting/src/lib.rs b/polkadot/node/core/approval-voting/src/lib.rs
index 7cea22d1a6a7..eb236f42fca2 100644
--- a/polkadot/node/core/approval-voting/src/lib.rs
+++ b/polkadot/node/core/approval-voting/src/lib.rs
@@ -2680,8 +2680,15 @@ where
 						Vec::new(),
 					)),
 			};
-			is_duplicate &= approval_entry.is_assigned(assignment.validator);
-			approval_entry.import_assignment(tranche, assignment.validator, tick_now);
+
+			let is_duplicate_for_candidate = approval_entry.is_assigned(assignment.validator);
+			is_duplicate &= is_duplicate_for_candidate;
+			approval_entry.import_assignment(
+				tranche,
+				assignment.validator,
+				tick_now,
+				is_duplicate_for_candidate,
+			);
 
 			// We've imported a new assignment, so we need to schedule a wake-up for when that might
 			// no-show.
diff --git a/polkadot/node/core/approval-voting/src/persisted_entries.rs b/polkadot/node/core/approval-voting/src/persisted_entries.rs
index d891af01c3ab..238e2c3706ea 100644
--- a/polkadot/node/core/approval-voting/src/persisted_entries.rs
+++ b/polkadot/node/core/approval-voting/src/persisted_entries.rs
@@ -172,7 +172,7 @@ impl ApprovalEntry {
 		});
 
 		our.map(|a| {
-			self.import_assignment(a.tranche(), a.validator_index(), tick_now);
+			self.import_assignment(a.tranche(), a.validator_index(), tick_now, false);
 
 			(a.cert().clone(), a.validator_index(), a.tranche())
 		})
@@ -197,6 +197,7 @@ impl ApprovalEntry {
 		tranche: DelayTranche,
 		validator_index: ValidatorIndex,
 		tick_now: Tick,
+		is_duplicate: bool,
 	) {
 		// linear search probably faster than binary. not many tranches typically.
 		let idx = match self.tranches.iter().position(|t| t.tranche >= tranche) {
@@ -213,8 +214,15 @@ impl ApprovalEntry {
 				self.tranches.len() - 1
 			},
 		};
-
-		self.tranches[idx].assignments.push((validator_index, tick_now));
+		// At restart we might have duplicate assignments because approval-distribution is not
+		// persistent across restarts, so avoid adding duplicates.
+		// We already know if we have seen an assignment from this validator and since this
+		// function is on the hot path we can avoid iterating through tranches by using
+		// !is_duplicate to determine if it is already present in the vector and does not need
+		// adding.
+		if !is_duplicate {
+			self.tranches[idx].assignments.push((validator_index, tick_now));
+		}
 		self.assigned_validators.set(validator_index.0 as _, true);
 	}
 
diff --git a/prdoc/pr_6971.prdoc b/prdoc/pr_6971.prdoc
new file mode 100644
index 000000000000..4790d773fee4
--- /dev/null
+++ b/prdoc/pr_6971.prdoc
@@ -0,0 +1,16 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Make importing of duplicate assignment idempotent
+
+doc:
+  - audience: Node Dev
+    description: |
+      Normally, approval-voting wouldn't receive duplicate assignments because approval-distribution makes
+      sure of it, however in the situation where we restart we might receive the same assignment again and
+      since approval-voting already persisted it we will end up inserting it twice in ApprovalEntry.tranches.assignments 
+      because that's an array. Fix this by inserting only assignments that are not duplicate.
+
+crates:
+  - name: polkadot-node-core-approval-voting
+    bump: minor