diff --git a/env_values.py b/env_values.py
deleted file mode 100644
index 20db913..0000000
--- a/env_values.py
+++ /dev/null
@@ -1,39 +0,0 @@
-import os
-from dotenv import find_dotenv, dotenv_values
-
-# Find an environment file, either given by the env `CY_ENV_FILE` or find a file
-# called `.env`. Same for goes for an override file.
-CY_ENV_FILE = os.environ.get('CY_ENV_FILE', find_dotenv('.env'))
-CY_ENV_OVERRIDE_FILE = os.environ.get('CY_ENV_OVERRIDE_FILE', find_dotenv('.env.override'))
-
-def env_values():
-    """Retrieve environment variables by combining `os.environ`, `CY_ENV_FILE` and `CY_ENV_OVERRIDE_FILE`.
-
-    Get environment variables by looking at (in order):
-        1. os.environ
-        2. .env.override
-        3. .env
-
-    When a variable is present in `os.environ` and `.env`, the one in `.env` will be ignored and the one in `os.environ`
-    will "win".
-
-    Calling `env_values()` has no side effects, eg `os.environ` not be altered.
-
-    Returns:
-        :dict: Env values.
-
-    Examples:
-        >>> env = env_values()
-        >>>
-        >>> env.get('CY_DEBUG')
-        >>> env.get('CY_DEBUG', False)
-        >>> env['CY_DEBUG']
-    """
-    env_file = dotenv_values(CY_ENV_FILE) if CY_ENV_FILE else {}
-    env_override_file = dotenv_values(CY_ENV_OVERRIDE_FILE) if CY_ENV_OVERRIDE_FILE else {}
-
-    return {
-        **env_file,
-        **env_override_file,
-        **os.environ,
-    }
diff --git a/env_values/__init__.py b/env_values/__init__.py
new file mode 100644
index 0000000..c7d9777
--- /dev/null
+++ b/env_values/__init__.py
@@ -0,0 +1 @@
+from .env_values import env_values
diff --git a/env_values/env_values.py b/env_values/env_values.py
new file mode 100644
index 0000000..eae5f96
--- /dev/null
+++ b/env_values/env_values.py
@@ -0,0 +1,75 @@
+from dotenv import dotenv_values
+import os
+import yaml
+
+def _gen_values(values, prefix=''):
+    for key, value in values.items():
+        yield (f'{prefix}{key}', value)
+        if isinstance(value, dict):
+            yield from _gen_values(value, prefix=f'{prefix}{key}_')
+
+def yaml_values(path):
+    """
+    Parse a JSON or YAML file and return its content as a dict.
+
+    The returned dict will contain all nested values on the
+    root level as well, identified by keys that are concatenations
+    of the keys of their ancestors.
+
+    For example, the following structure will produce four values:
+    `FOO`, `FOO_BAR`, `FOO_BAR_BAZ`, and `BAZ`.
+    ```
+    FOO:
+      BAR:
+        BAZ: baz
+    FOO_BAR: 1337
+    BAZ: ['foo', 'bar']
+    ```
+
+    Parameters:
+        path: Absolute or relative path to the file.
+    """
+    with open(path) as f:
+        values = yaml.safe_load(f)
+    if not isinstance(values, dict):
+        return {}
+    return dict(_gen_values(values))
+
+def env_values(*paths):
+    """Retrieve environment variables by combining `os.environ` and the provided env files.
+
+    Get environment variables by looking at (in order):
+        1. os.environ
+        2. file #n
+        3. file #n-1
+        ...
+      n+1. file #1
+
+    When a variable is present in `os.environ` and any of the files, the ones in the files will be ignored and the one in `os.environ`
+    will "win".
+
+    Calling `env_values()` has no side effects, eg `os.environ` not be altered.
+
+    Returns:
+        :dict: Env values.
+
+    Example:
+        >>> env = env_values('.env')
+        >>>
+        >>> env.get('CY_DEBUG')
+        >>> env.get('CY_DEBUG', False)
+        >>> env['CY_DEBUG']
+    """
+    values = {}
+    for path in paths:
+        if not path:
+            continue
+        if path.endswith('.json') or path.endswith('.yml') or path.endswith('.yaml'):
+            values.update(yaml_values(path))
+        else:
+            values.update(dotenv_values(path))
+    
+    return {
+        **values,
+        **os.environ
+    }
diff --git a/setup.py b/setup.py
index f7eb797..d0b748d 100644
--- a/setup.py
+++ b/setup.py
@@ -1,14 +1,15 @@
 from setuptools import setup
 
-version = '1.0'
+version = '2.0'
+
+with open("README.md") as f:
+    long_description = f.read()
 
 setup(
     name='env_values',
     version=version,
     description="Load env values",
-    long_description='\n'.join([
-        open("README.md").read(),
-    ]),
+    long_description=long_description,
     keywords='env',
     author='Burhan Zainuddin',
     author_email='burhan@codeyellow.nl',
@@ -19,6 +20,6 @@
     python_requires='~=3.3',
     include_package_data=True,
     zip_safe=True,
-    install_requires=['python-dotenv'],
+    install_requires=['python-dotenv', 'pyyaml'],
     py_modules=['env_values'],
 )
\ No newline at end of file
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..c0fa5e5
--- /dev/null
+++ b/tests/__init__.py
@@ -0,0 +1,2 @@
+from .test_env import *
+from .test_yaml import *
diff --git a/tests/fixtures/nested.env b/tests/fixtures/nested.env
new file mode 100644
index 0000000..85f7a51
--- /dev/null
+++ b/tests/fixtures/nested.env
@@ -0,0 +1,8 @@
+FOO_BAR=FOOBAR
+FOO_BAR_BAZ=FOOBARBAZ
+BAR_BAZ=BAZ
+BAR_BAZ=BARBAZ
+BAZ=BAZ
+BAZ_69_1337=LEET
+BAZ_69_False=False
+BAZ_69_None
diff --git a/tests/fixtures/nested.yml b/tests/fixtures/nested.yml
new file mode 100644
index 0000000..5e0ef54
--- /dev/null
+++ b/tests/fixtures/nested.yml
@@ -0,0 +1,11 @@
+FOO:
+  BAR:
+    BAZ: foobarbaz
+BAR:
+  BAZ: barbaz
+BAR_BAZ: baz
+BAZ:
+  69:
+    1337: '1337'
+    true: 'True'
+    null: 'None'
diff --git a/tests/fixtures/simple.env b/tests/fixtures/simple.env
new file mode 100644
index 0000000..cf1d426
--- /dev/null
+++ b/tests/fixtures/simple.env
@@ -0,0 +1,7 @@
+FOO=FOO
+BAR=123
+QUX=1.23
+FOO_BAR=false
+FOO_QUX=null
+FOO_BAR_BAZ=foo,bar,baz
+# TEST=TEST
diff --git a/tests/fixtures/simple.yml b/tests/fixtures/simple.yml
new file mode 100644
index 0000000..7198d0e
--- /dev/null
+++ b/tests/fixtures/simple.yml
@@ -0,0 +1,7 @@
+FOO: foo
+BAR: 123
+BAZ: 1.23
+FOO_BAR: false
+FOO_BAZ: null
+FOO_BAR_BAZ: ['foo', 'bar', 'baz']
+# TEST: test
diff --git a/tests/test_env.py b/tests/test_env.py
new file mode 100644
index 0000000..c124df6
--- /dev/null
+++ b/tests/test_env.py
@@ -0,0 +1,133 @@
+import os
+import unittest
+from env_values import *
+    
+class OverrideTest(unittest.TestCase):
+    
+    def test_yaml_dotenv(self):
+        env = env_values(
+            'tests/fixtures/simple.yml',
+            'tests/fixtures/simple.env'
+        )
+        self.assertEqual(env['FOO'], 'FOO')
+        self.assertEqual(env['BAR'], '123')
+        self.assertEqual(env['BAZ'], 1.23)
+        self.assertEqual(env['QUX'], '1.23')
+        self.assertEqual(env['FOO_BAR'], 'false')
+        self.assertEqual(env['FOO_BAZ'], None)
+        self.assertEqual(env['FOO_QUX'], 'null')
+        self.assertEqual(env['FOO_BAR_BAZ'], 'foo,bar,baz')
+        self.assertFalse('TEST' in env)
+    
+    def test_dotenv_yaml(self):
+        env = env_values(
+            'tests/fixtures/simple.env',
+            'tests/fixtures/simple.yml',
+        )
+        self.assertEqual(env['FOO'], 'foo')
+        self.assertEqual(env['BAR'], 123)
+        self.assertEqual(env['BAZ'], 1.23)
+        self.assertEqual(env['QUX'], '1.23')
+        self.assertEqual(env['FOO_BAR'], False)
+        self.assertEqual(env['FOO_BAZ'], None)
+        self.assertEqual(env['FOO_QUX'], 'null')
+        self.assertEqual(env['FOO_BAR_BAZ'], ['foo', 'bar', 'baz'])
+        self.assertFalse('TEST' in env)
+
+class NestedOverrideTest(unittest.TestCase):
+    
+    def setUp(self):
+        self.env = env_values(
+            'tests/fixtures/nested.yml',
+            'tests/fixtures/nested.env',
+        )
+    
+    def test_nesting(self):
+        self.assertEqual(self.env['FOO'], {'BAR': {'BAZ': 'foobarbaz'}})
+        self.assertEqual(self.env['FOO_BAR'], 'FOOBAR')
+        self.assertEqual(self.env['FOO_BAR_BAZ'], 'FOOBARBAZ')
+    
+    def test_duplicate_keys(self):
+        self.assertEqual(self.env['BAR'], {'BAZ': 'barbaz'})
+        self.assertNotEqual(self.env['BAR_BAZ'], 'barbaz')
+        self.assertNotEqual(self.env['BAR_BAZ'], 'baz')
+        self.assertNotEqual(self.env['BAR_BAZ'], 'BAZ')
+        self.assertEqual(self.env['BAR_BAZ'], 'BARBAZ')
+    
+    def test_nonstring_keys(self):
+        self.assertEqual(self.env['BAZ'], 'BAZ')
+        self.assertEqual(self.env['BAZ_69'], {1337: '1337', True: 'True', None: 'None'})
+        self.assertEqual(self.env['BAZ_69_1337'], 'LEET')
+        self.assertEqual(self.env['BAZ_69_True'], 'True')
+        self.assertEqual(self.env['BAZ_69_False'], 'False')
+        self.assertEqual(self.env['BAZ_69_None'], None)
+
+class OsEnvTest(unittest.TestCase):
+
+    def test_loading(self):
+        environ = os.environ.copy()
+        env_values(
+            'tests/fixtures/simple.yml',
+            'tests/fixtures/simple.env',
+        )
+        self.assertEqual(os.environ, environ)
+    
+    def test_env(self):
+        os.environ.update({
+            'FOO': 'foo',
+            'BAR': 'bar',
+            'FOO_BAR': 'foo_bar',
+            'FOO_BAR_BAZ': 'foo_bar_baz',
+            'TEST': 'test',
+        })
+        env = env_values()
+        self.assertEqual(env['FOO'], 'foo')
+        self.assertEqual(env['BAR'], 'bar')
+        self.assertEqual(env['FOO_BAR'], 'foo_bar')
+        self.assertEqual(env['FOO_BAR_BAZ'], 'foo_bar_baz')
+        self.assertEqual(env['TEST'], 'test')
+        os.environ.clear()
+    
+    def test_yaml_env(self):
+        os.environ.update({
+            'FOO': 'foo',
+            'BAR': 'bar',
+            'QUX': 'qux',
+            'FOO_BAR': 'foo_bar',
+            'FOO_QUX': 'foo_qux',
+            'FOO_BAR_BAZ': 'foo_bar_baz',
+            'TEST': 'test',
+        })
+        env = env_values('tests/fixtures/simple.yml')
+        self.assertEqual(env['FOO'], 'foo')
+        self.assertEqual(env['BAR'], 'bar')
+        self.assertEqual(env['BAZ'], 1.23)
+        self.assertEqual(env['QUX'], 'qux')
+        self.assertEqual(env['FOO_BAR'], 'foo_bar')
+        self.assertEqual(env['FOO_BAZ'], None)
+        self.assertEqual(env['FOO_QUX'], 'foo_qux')
+        self.assertEqual(env['FOO_BAR_BAZ'], 'foo_bar_baz')
+        self.assertEqual(env['TEST'], 'test')
+        os.environ.clear()
+    
+    def test_dotenv_env(self):
+        os.environ.update({
+            'FOO': 'foo',
+            'BAR': 'bar',
+            'BAZ': 'baz',
+            'FOO_BAR': 'foo_bar',
+            'FOO_BAZ': 'foo_baz',
+            'FOO_BAR_BAZ': 'foo_bar_baz',
+            'TEST': 'test',
+        })
+        env = env_values('tests/fixtures/simple.env')
+        self.assertEqual(env['FOO'], 'foo')
+        self.assertEqual(env['BAR'], 'bar')
+        self.assertEqual(env['BAZ'], 'baz')
+        self.assertEqual(env['QUX'], '1.23')
+        self.assertEqual(env['FOO_BAR'], 'foo_bar')
+        self.assertEqual(env['FOO_BAZ'], 'foo_baz')
+        self.assertEqual(env['FOO_QUX'], 'null')
+        self.assertEqual(env['FOO_BAR_BAZ'], 'foo_bar_baz')
+        self.assertEqual(env['TEST'], 'test')
+        os.environ.clear()
diff --git a/tests/test_yaml.py b/tests/test_yaml.py
new file mode 100644
index 0000000..a0f125f
--- /dev/null
+++ b/tests/test_yaml.py
@@ -0,0 +1,38 @@
+import unittest
+from env_values import *
+
+class SimpleYamlTest(unittest.TestCase):
+    
+    def setUp(self):
+        self.env = env_values('tests/fixtures/simple.yml')
+    
+    def test_values(self):
+        self.assertEqual(self.env['FOO'], 'foo')
+        self.assertEqual(self.env['BAR'], 123)
+        self.assertEqual(self.env['BAZ'], 1.23)
+        self.assertEqual(self.env['FOO_BAR'], False)
+        self.assertEqual(self.env['FOO_BAZ'], None)
+        self.assertEqual(self.env['FOO_BAR_BAZ'], ['foo', 'bar', 'baz'])
+        self.assertFalse('TEST' in self.env)
+    
+class NestedYamlTest(unittest.TestCase):
+    
+    def setUp(self):
+        self.env = env_values('tests/fixtures/nested.yml')
+    
+    def test_nesting(self):
+        self.assertEqual(self.env['FOO'], {'BAR': {'BAZ': 'foobarbaz'}})
+        self.assertEqual(self.env['FOO_BAR'], {'BAZ': 'foobarbaz'})
+        self.assertEqual(self.env['FOO_BAR_BAZ'], 'foobarbaz')
+    
+    def test_duplicate_keys(self):
+        self.assertEqual(self.env['BAR'], {'BAZ': 'barbaz'})
+        self.assertNotEqual(self.env['BAR_BAZ'], 'barbaz')
+        self.assertEqual(self.env['BAR_BAZ'], 'baz')
+    
+    def test_nonstring_keys(self):
+        self.assertEqual(self.env['BAZ'], {69: {1337: '1337', True: 'True', None: 'None'}})
+        self.assertEqual(self.env['BAZ_69'], {1337: '1337', True: 'True', None: 'None'})
+        self.assertEqual(self.env['BAZ_69_1337'], '1337')
+        self.assertEqual(self.env['BAZ_69_True'], 'True')
+        self.assertEqual(self.env['BAZ_69_None'], 'None')