diff --git a/ibis/backends/duckdb/registry.py b/ibis/backends/duckdb/registry.py
index 26d0a12ec2f0..9e346560aff6 100644
--- a/ibis/backends/duckdb/registry.py
+++ b/ibis/backends/duckdb/registry.py
@@ -496,6 +496,7 @@ def _to_json_collection(t, op):
         ops.TimestampDelta: _temporal_delta,
         ops.ToJSONMap: _to_json_collection,
         ops.ToJSONArray: _to_json_collection,
+        ops.ArrayFlatten: unary(sa.func.flatten),
     }
 )