diff --git a/tests/test_encoder.py b/tests/test_encoder.py
index 7f59f25..c9d5643 100644
--- a/tests/test_encoder.py
+++ b/tests/test_encoder.py
@@ -88,6 +88,17 @@ def test_encode_primitive_array():
     result = encode(data)
     assert result == 'items: [hello,"world, test",foo]'
 
+def test_encode_tuple_array():
+    """Test encoding of primitive arrays."""
+    # Number tuple
+    assert encode({'numbers': (1, 2, 3)}) == 'numbers: [1,2,3]'
+    
+    # String tuple
+    assert encode({'names': ('Alice', 'Bob')}) == 'names: [Alice,Bob]'
+    
+    # Mixed primitive tuple
+    assert encode({'mixed': (1, 'text', True, None)}) == 'mixed: [1,text,true,null]'
+
 
 def test_encode_array_delimiter():
     """Test different array delimiters."""
diff --git a/toon/encoder.py b/toon/encoder.py
index 6e1206c..05c410a 100644
--- a/toon/encoder.py
+++ b/toon/encoder.py
@@ -117,9 +117,11 @@ def _encode_value(value: Any, level: int, opts: EncoderOptions) -> str:
         return _encode_array(value, level, opts)
     elif isinstance(value, dict):
         return _encode_object(value, level, opts)
+    elif isinstance(value, tuple):
+        return _encode_tuple(value)
     else:
-        # Handle other types as null
-        return 'null'
+        # Handle other types with NotImplementedError
+        raise NotImplementedError(f'Encoding for type {type(value)} is not implemented.')
 
 
 def _encode_object(obj: dict, level: int, opts: EncoderOptions) -> str:
@@ -177,6 +179,16 @@ def _encode_array(arr: list, level: int, opts: EncoderOptions) -> str:
     # Mixed array (list format)
     return _encode_list_array(arr, level, opts, key=None)
 
+def _encode_tuple(value: tuple) -> str:
+    """Encode a tuple."""
+    if not value:
+        return '[]'
+    
+    tuple_data = ','.join(_encode_primitive_value(v) for v in value)
+    tuple_string = f'[{tuple_data}]'
+
+    return tuple_string
+
 
 def _encode_array_with_key(key: str, arr: list, level: int, opts: EncoderOptions) -> str:
     """Encode an array with its key prefix for object context."""