diff --git a/pageserver/src/http/routes.rs b/pageserver/src/http/routes.rs
index cb7c2b60ef..f18f0b730c 100644
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -324,6 +324,9 @@ impl From<crate::tenant::TimelineArchivalError> for ApiError {
         match value {
             NotFound => ApiError::NotFound(anyhow::anyhow!("timeline not found").into()),
             Timeout => ApiError::Timeout("hit pageserver internal timeout".into()),
+            e @ HasArchivedParent(_) => {
+                ApiError::PreconditionFailed(e.to_string().into_boxed_str())
+            }
             HasUnarchivedChildren(children) => ApiError::PreconditionFailed(
                 format!(
                     "Cannot archive timeline which has non-archived child timelines: {children:?}"
diff --git a/pageserver/src/tenant.rs b/pageserver/src/tenant.rs
index 60ab242ffc..fb30857ddf 100644
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -509,6 +509,9 @@ pub enum TimelineArchivalError {
     #[error("Timeout")]
     Timeout,
 
+    #[error("ancestor is archived: {}", .0)]
+    HasArchivedParent(TimelineId),
+
     #[error("HasUnarchivedChildren")]
     HasUnarchivedChildren(Vec<TimelineId>),
 
@@ -524,6 +527,7 @@ impl Debug for TimelineArchivalError {
         match self {
             Self::NotFound => write!(f, "NotFound"),
             Self::Timeout => write!(f, "Timeout"),
+            Self::HasArchivedParent(p) => f.debug_tuple("HasArchivedParent").field(p).finish(),
             Self::HasUnarchivedChildren(c) => {
                 f.debug_tuple("HasUnarchivedChildren").field(c).finish()
             }
@@ -1369,11 +1373,20 @@ impl Tenant {
         let timeline = {
             let timelines = self.timelines.lock().unwrap();
 
-            let timeline = match timelines.get(&timeline_id) {
-                Some(t) => t,
-                None => return Err(TimelineArchivalError::NotFound),
+            let Some(timeline) = timelines.get(&timeline_id) else {
+                return Err(TimelineArchivalError::NotFound);
             };
 
+            if state == TimelineArchivalState::Unarchived {
+                if let Some(ancestor_timeline) = timeline.ancestor_timeline() {
+                    if ancestor_timeline.is_archived() == Some(true) {
+                        return Err(TimelineArchivalError::HasArchivedParent(
+                            ancestor_timeline.timeline_id,
+                        ));
+                    }
+                }
+            }
+
             // Ensure that there are no non-archived child timelines
             let children: Vec<TimelineId> = timelines
                 .iter()
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 8096a0d18c..63d59e06a5 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -867,6 +867,11 @@ impl Timeline {
             .map(|ancestor| ancestor.timeline_id)
     }
 
+    /// Get the ancestor timeline
+    pub(crate) fn ancestor_timeline(&self) -> Option<&Arc<Timeline>> {
+        self.ancestor_timeline.as_ref()
+    }
+
     /// Get the bytes written since the PITR cutoff on this branch, and
     /// whether this branch's ancestor_lsn is within its parent's PITR.
     pub(crate) fn get_pitr_history_stats(&self) -> (u64, bool) {
diff --git a/test_runner/regress/test_timeline_archive.py b/test_runner/regress/test_timeline_archive.py
index b774c7c9fe..7f158ad251 100644
--- a/test_runner/regress/test_timeline_archive.py
+++ b/test_runner/regress/test_timeline_archive.py
@@ -94,3 +94,29 @@ def test_timeline_archive(neon_simple_env: NeonEnv):
         timeline_id=parent_timeline_id,
         state=TimelineArchivalState.ARCHIVED,
     )
+
+    # Test that the leaf can't be unarchived
+    with pytest.raises(
+        PageserverApiException,
+        match="ancestor is archived",
+    ) as exc:
+        assert timeline_path.exists()
+
+        ps_http.timeline_archival_config(
+            tenant_id=env.initial_tenant,
+            timeline_id=leaf_timeline_id,
+            state=TimelineArchivalState.UNARCHIVED,
+        )
+
+    # Unarchive works for the leaf if the parent gets unarchived first
+    ps_http.timeline_archival_config(
+        tenant_id=env.initial_tenant,
+        timeline_id=parent_timeline_id,
+        state=TimelineArchivalState.UNARCHIVED,
+    )
+
+    ps_http.timeline_archival_config(
+        tenant_id=env.initial_tenant,
+        timeline_id=leaf_timeline_id,
+        state=TimelineArchivalState.UNARCHIVED,
+    )