diff --git a/pkg/ccl/backupccl/testdata/backup-restore/show_backup b/pkg/ccl/backupccl/testdata/backup-restore/show_backup
index 3328738e5b31..5811ee1f095a 100644
--- a/pkg/ccl/backupccl/testdata/backup-restore/show_backup
+++ b/pkg/ccl/backupccl/testdata/backup-restore/show_backup
@@ -4,6 +4,15 @@
 new-cluster name=s1 allow-implicit-access localities=eu-central-1,eu-north-1,us-east-1
 ----
 
+link-backup cluster=s1 src-path=show_backup_validate,invalidDependOnBy_21.1 dest-path=invalidDependOnBy_21.1
+----
+
+# This backup intentionally has a dangling invalid depend on by reference.
+query-sql regex=invalid\sdepended-on-by
+SELECT * FROM [SHOW BACKUP VALIDATE FROM 'invalidDependOnBy_21.1' IN 'nodelocal://1/'];
+----
+true
+
 link-backup cluster=s1 src-path=show_backup_validate,valid-22.2 dest-path=valid-22.2
 ----
 
diff --git a/pkg/ccl/backupccl/testdata/show_backup_validate/invalidDependOnBy_21.1/BACKUP_MANIFEST b/pkg/ccl/backupccl/testdata/show_backup_validate/invalidDependOnBy_21.1/BACKUP_MANIFEST
new file mode 100644
index 000000000000..07ed4fc32828
Binary files /dev/null and b/pkg/ccl/backupccl/testdata/show_backup_validate/invalidDependOnBy_21.1/BACKUP_MANIFEST differ
diff --git a/pkg/ccl/backupccl/testdata/show_backup_validate/invalidDependOnBy_21.1/BACKUP_MANIFEST-CHECKSUM b/pkg/ccl/backupccl/testdata/show_backup_validate/invalidDependOnBy_21.1/BACKUP_MANIFEST-CHECKSUM
new file mode 100644
index 000000000000..70747a396825
--- /dev/null
+++ b/pkg/ccl/backupccl/testdata/show_backup_validate/invalidDependOnBy_21.1/BACKUP_MANIFEST-CHECKSUM
@@ -0,0 +1 @@
+'Üóÿ
\ No newline at end of file
diff --git a/pkg/sql/catalog/post_deserialization_changes.go b/pkg/sql/catalog/post_deserialization_changes.go
index 191588f12491..5d6b51df449b 100644
--- a/pkg/sql/catalog/post_deserialization_changes.go
+++ b/pkg/sql/catalog/post_deserialization_changes.go
@@ -82,6 +82,10 @@ const (
 	// references.
 	RemovedDuplicateIDsInRefs
 
+	// AddedConstraintIDs indicates that table descriptors had constraint ID
+	// added.
+	AddedConstraintIDs
+
 	// RemovedSelfEntryInSchemas corresponds to a change which occurred in
 	// database descriptors to recover from an earlier bug whereby when
 	// dropping a schema, we'd mark the database itself as though it was the
diff --git a/pkg/sql/catalog/tabledesc/table_desc_builder.go b/pkg/sql/catalog/tabledesc/table_desc_builder.go
index c168f5fdd346..6a72c2e8d1fa 100644
--- a/pkg/sql/catalog/tabledesc/table_desc_builder.go
+++ b/pkg/sql/catalog/tabledesc/table_desc_builder.go
@@ -178,6 +178,16 @@ func (tdb *tableDescriptorBuilder) RunRestoreChanges(
 		tdb.changes.Add(catalog.UpgradedSequenceReference)
 	}
 
+	// All backups taken in versions 22.1 and later should already have
+	// constraint IDs set. Technically, now that we are in v24.1, we no longer
+	// support restoring from versions older than 22.1, but we still have
+	// tests that restore from old versions. Until those fixtures are updated,
+	// we need to handle the case where constraint IDs are not set already.
+	// TODO(rafi): remove this once all fixtures are updated. See: https://github.com/cockroachdb/cockroach/issues/120146.
+	if changed := maybeAddConstraintIDs(tdb.maybeModified); changed {
+		tdb.changes.Add(catalog.AddedConstraintIDs)
+	}
+
 	// Upgrade the declarative schema changer state
 	if scpb.MigrateDescriptorState(version, tdb.maybeModified.ParentID, tdb.maybeModified.DeclarativeSchemaChangerState) {
 		tdb.changes.Add(catalog.UpgradedDeclarativeSchemaChangerState)
@@ -778,6 +788,102 @@ func maybeFixPrimaryIndexEncoding(idx *descpb.IndexDescriptor) (hasChanged bool)
 	return true
 }
 
+// maybeAddConstraintIDs ensures that all constraints have an ID associated with
+// them.
+func maybeAddConstraintIDs(desc *descpb.TableDescriptor) (hasChanged bool) {
+	// Only assign constraint IDs to physical tables.
+	if !desc.IsTable() {
+		return false
+	}
+	// Collect pointers to constraint ID variables.
+	var idPtrs []*descpb.ConstraintID
+	if len(desc.PrimaryIndex.KeyColumnIDs) > 0 {
+		idPtrs = append(idPtrs, &desc.PrimaryIndex.ConstraintID)
+	}
+	for i := range desc.Indexes {
+		idx := &desc.Indexes[i]
+		if !idx.Unique || idx.UseDeletePreservingEncoding {
+			continue
+		}
+		idPtrs = append(idPtrs, &idx.ConstraintID)
+	}
+	checkByName := make(map[string]*descpb.TableDescriptor_CheckConstraint)
+	for i := range desc.Checks {
+		ck := desc.Checks[i]
+		idPtrs = append(idPtrs, &ck.ConstraintID)
+		checkByName[ck.Name] = ck
+	}
+	fkByName := make(map[string]*descpb.ForeignKeyConstraint)
+	for i := range desc.OutboundFKs {
+		fk := &desc.OutboundFKs[i]
+		idPtrs = append(idPtrs, &fk.ConstraintID)
+		fkByName[fk.Name] = fk
+	}
+	for i := range desc.InboundFKs {
+		idPtrs = append(idPtrs, &desc.InboundFKs[i].ConstraintID)
+	}
+	uwoiByName := make(map[string]*descpb.UniqueWithoutIndexConstraint)
+	for i := range desc.UniqueWithoutIndexConstraints {
+		uwoi := &desc.UniqueWithoutIndexConstraints[i]
+		idPtrs = append(idPtrs, &uwoi.ConstraintID)
+		uwoiByName[uwoi.Name] = uwoi
+	}
+	for _, m := range desc.GetMutations() {
+		if idx := m.GetIndex(); idx != nil && idx.Unique && !idx.UseDeletePreservingEncoding {
+			idPtrs = append(idPtrs, &idx.ConstraintID)
+		} else if c := m.GetConstraint(); c != nil {
+			switch c.ConstraintType {
+			case descpb.ConstraintToUpdate_CHECK, descpb.ConstraintToUpdate_NOT_NULL:
+				idPtrs = append(idPtrs, &c.Check.ConstraintID)
+			case descpb.ConstraintToUpdate_FOREIGN_KEY:
+				idPtrs = append(idPtrs, &c.ForeignKey.ConstraintID)
+			case descpb.ConstraintToUpdate_UNIQUE_WITHOUT_INDEX:
+				idPtrs = append(idPtrs, &c.UniqueWithoutIndexConstraint.ConstraintID)
+			}
+		}
+	}
+	// Set constraint ID counter to sane initial value.
+	var maxID descpb.ConstraintID
+	for _, p := range idPtrs {
+		if id := *p; id > maxID {
+			maxID = id
+		}
+	}
+	if desc.NextConstraintID <= maxID {
+		desc.NextConstraintID = maxID + 1
+		hasChanged = true
+	}
+	// Update zero constraint IDs using counter.
+	for _, p := range idPtrs {
+		if *p != 0 {
+			continue
+		}
+		*p = desc.NextConstraintID
+		desc.NextConstraintID++
+		hasChanged = true
+	}
+	// Reconcile constraint IDs between enforced slice and mutation.
+	for _, m := range desc.GetMutations() {
+		if c := m.GetConstraint(); c != nil {
+			switch c.ConstraintType {
+			case descpb.ConstraintToUpdate_CHECK, descpb.ConstraintToUpdate_NOT_NULL:
+				if other, ok := checkByName[c.Check.Name]; ok {
+					c.Check.ConstraintID = other.ConstraintID
+				}
+			case descpb.ConstraintToUpdate_FOREIGN_KEY:
+				if other, ok := fkByName[c.ForeignKey.Name]; ok {
+					c.ForeignKey.ConstraintID = other.ConstraintID
+				}
+			case descpb.ConstraintToUpdate_UNIQUE_WITHOUT_INDEX:
+				if other, ok := uwoiByName[c.UniqueWithoutIndexConstraint.Name]; ok {
+					c.UniqueWithoutIndexConstraint.ConstraintID = other.ConstraintID
+				}
+			}
+		}
+	}
+	return hasChanged
+}
+
 // maybeRemoveDuplicateIDsInRefs ensures that IDs in references to other tables
 // are not duplicated.
 func maybeRemoveDuplicateIDsInRefs(d *descpb.TableDescriptor) (hasChanged bool) {