diff --git a/.changes/unreleased/Under the Hood-20241205-143144.yaml b/.changes/unreleased/Under the Hood-20241205-143144.yaml
new file mode 100644
index 00000000000..10aa90a2b2a
--- /dev/null
+++ b/.changes/unreleased/Under the Hood-20241205-143144.yaml	
@@ -0,0 +1,7 @@
+kind: Under the Hood
+body: Improve selection peformance by optimizing the select_children() and select_parents()
+  functions.
+time: 2024-12-05T14:31:44.584216-05:00
+custom:
+  Author: peterallenwebb
+  Issue: "11099"
diff --git a/core/dbt/graph/graph.py b/core/dbt/graph/graph.py
index cf569f3547d..4d1e545cbd2 100644
--- a/core/dbt/graph/graph.py
+++ b/core/dbt/graph/graph.py
@@ -67,8 +67,14 @@ def select_children(
         while len(selected) > 0 and (max_depth is None or i < max_depth):
             next_layer: Set[UniqueId] = set()
             for node in selected:
-                next_layer.update(self.descendants(node, 1))
-            next_layer = next_layer - children  # Avoid re-searching
+                next_layer.update(
+                    iter(
+                        e[1]
+                        for e in self.graph.out_edges(node)
+                        if e[1] not in children
+                        and self.filter_edges_by_type(e[0], e[1], "parent_test")
+                    )
+                )
             children.update(next_layer)
             selected = next_layer
             i += 1
@@ -86,8 +92,14 @@ def select_parents(
         while len(selected) > 0 and (max_depth is None or i < max_depth):
             next_layer: Set[UniqueId] = set()
             for node in selected:
-                next_layer.update(self.ancestors(node, 1))
-            next_layer = next_layer - parents  # Avoid re-searching
+                next_layer.update(
+                    iter(
+                        e[0]
+                        for e in self.graph.in_edges(node)
+                        if e[0] not in parents
+                        and self.filter_edges_by_type(e[0], e[1], "parent_test")
+                    )
+                )
             parents.update(next_layer)
             selected = next_layer
             i += 1