diff --git a/src/connector/codec/src/decoder/avro/mod.rs b/src/connector/codec/src/decoder/avro/mod.rs
index 71bb430059d87..a001531019759 100644
--- a/src/connector/codec/src/decoder/avro/mod.rs
+++ b/src/connector/codec/src/decoder/avro/mod.rs
@@ -108,9 +108,17 @@ impl<'a> AvroParseOptions<'a> {
 
         let v: ScalarImpl = match (type_expected, value) {
             (_, Value::Null) => return Ok(DatumCow::NULL),
-            // ---- Union -----
+            // ---- Union (with >=2 non null variants) -----
             (DataType::Struct(struct_type_info), Value::Union(variant, v)) => match self.schema {
                 Some(Schema::Union(u)) => {
+                    if let Some(inner) = get_nullable_union_inner(u) {
+                        // nullable Union ([null, record])
+                        return Self {
+                            schema: Some(inner),
+                            relax_numeric: self.relax_numeric,
+                        }
+                        .convert_to_datum(v, type_expected);
+                    }
                     let variant_schema = &u.variants()[*variant as usize];
 
                     if matches!(variant_schema, &Schema::Null) {
@@ -144,7 +152,7 @@ impl<'a> AvroParseOptions<'a> {
                 }
                 _ => Err(create_error())?,
             },
-            // nullable Union
+            // nullable Union ([null, T])
             (_, Value::Union(_, v)) => {
                 let schema = self.extract_inner_schema(None);
                 return Self {