diff --git a/python/ray/dataframe/__init__.py b/python/ray/dataframe/__init__.py
index 6ba12b91a..6edc2804d 100644
--- a/python/ray/dataframe/__init__.py
+++ b/python/ray/dataframe/__init__.py
@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
+import threading
 
 DEFAULT_NPARTITIONS = 10
 
@@ -26,3 +27,10 @@ __all__ = [
     "DataFrame", "from_pandas", "to_pandas", "Series", "read_csv",
     "read_parquet"
 ]
+
+try:
+    if threading.current_thread().name == "MainThread":
+        import ray
+        ray.init()
+except AssertionError:
+    pass
diff --git a/python/ray/dataframe/test/test_dataframe.py b/python/ray/dataframe/test/test_dataframe.py
index 31087066a..64567ffdf 100644
--- a/python/ray/dataframe/test/test_dataframe.py
+++ b/python/ray/dataframe/test/test_dataframe.py
@@ -5,7 +5,6 @@ from __future__ import print_function
 import pytest
 import numpy as np
 import pandas as pd
-import ray
 import ray.dataframe as rdf
 
 
@@ -145,7 +144,6 @@ def create_test_dataframe():
 
 
 def test_int_dataframe():
-    ray.init()
 
     pandas_df = pd.DataFrame({'col1': [0, 1, 2, 3],
                               'col2': [4, 5, 6, 7],
diff --git a/python/ray/dataframe/test/test_io.py b/python/ray/dataframe/test/test_io.py
index 64ea2c0ff..0f2cc57ac 100644
--- a/python/ray/dataframe/test/test_io.py
+++ b/python/ray/dataframe/test/test_io.py
@@ -5,7 +5,6 @@ from __future__ import print_function
 import pytest
 import numpy as np
 import pandas as pd
-import ray
 import ray.dataframe as rdf
 import ray.dataframe.io as io
 import os
@@ -58,7 +57,6 @@ def teardown_csv_file():
 
 
 def test_from_parquet_small():
-    ray.init()
 
     setup_parquet_file(SMALL_ROW_SIZE)
 
diff --git a/python/ray/dataframe/test/test_series.py b/python/ray/dataframe/test/test_series.py
index 7db0d4d35..ba8b50061 100644
--- a/python/ray/dataframe/test/test_series.py
+++ b/python/ray/dataframe/test/test_series.py
@@ -4,9 +4,6 @@ from __future__ import print_function
 
 import pytest
 import ray.dataframe as rdf
-import ray
-
-ray.init()
 
 
 @pytest.fixture