diff --git a/src/arrayish_vec.rs b/src/arrayish_vec.rs
index 9e288d7..9a98c2c 100644
--- a/src/arrayish_vec.rs
+++ b/src/arrayish_vec.rs
@@ -42,7 +42,19 @@ impl<A: Arrayish> IndexMut<usize> for ArrayishVec<A> {
 }
 
 impl<A: Arrayish> ArrayishVec<A> {
-  // TODO(Vec): append
+  #[inline]
+  pub fn append(&mut self, other: &mut Self) {
+    let final_len = self.len + other.len;
+    if final_len > A::CAPACITY {
+      panic!("ArrayishVec: overflow!");
+    }
+    let target_slice = &mut self.data.slice_mut()[self.len..final_len];
+    for (target_mut, app_mut) in target_slice.iter_mut().zip(other.deref_mut()) {
+      replace(target_mut, replace(app_mut, A::Item::default()));
+    }
+    self.len = final_len;
+    other.len = 0;
+  }
 
   #[inline(always)]
   #[must_use]
diff --git a/tests/basic_tests.rs b/tests/basic_tests.rs
index c85c945..6c03891 100644
--- a/tests/basic_tests.rs
+++ b/tests/basic_tests.rs
@@ -97,3 +97,19 @@ fn ArrayishVec_iteration() {
   let av2: ArrayishVec<[i32; 4]> = av.clone().into_iter().collect();
   assert_eq!(av, av2);
 }
+
+#[test]
+fn ArrayishVec_append() {
+  let mut av: ArrayishVec<[i32; 10]> = Default::default();
+  av.push(1);
+  av.push(2);
+  av.push(3);
+  let mut av2: ArrayishVec<[i32; 10]> = Default::default();
+  av2.push(4);
+  av2.push(5);
+  av2.push(6);
+  //
+  av.append(&mut av2);
+  assert_eq!(av.as_slice(), &[1_i32, 2, 3, 4, 5, 6]);
+  assert_eq!(av2.as_slice(), &[]);
+}