diff --git a/CHANGELOG.md b/CHANGELOG.md
index b8991cc..ab8af55 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and uses [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Fixed
 * Copernicus DEM for NISAR URLs to fix 404 errors.
+* Support for EARTHDATA credentials passed as env vars.
 
 ## [0.5.3]
 
diff --git a/src/multirtc/__main__.py b/src/multirtc/__main__.py
index d0273fb..707c9b1 100644
--- a/src/multirtc/__main__.py
+++ b/src/multirtc/__main__.py
@@ -1,10 +1,17 @@
 import argparse
+import os
 
 from multirtc import dem, geocode, multirtc
+from multirtc.fetch import write_credentials_to_netrc_file
 from multirtc.multimetric import ale, point_target, rle
 
 
 def main():
+    username = os.getenv('EARTHDATA_USERNAME')
+    password = os.getenv('EARTHDATA_PASSWORD')
+    if username and password:
+        write_credentials_to_netrc_file(username, password, append=False)
+
     global_parser = argparse.ArgumentParser(
         prog='multirtc',
         description='ISCE3-based multi-sensor RTC and cal/val tool',
diff --git a/src/multirtc/fetch.py b/src/multirtc/fetch.py
index ba3516a..f779632 100644
--- a/src/multirtc/fetch.py
+++ b/src/multirtc/fetch.py
@@ -11,6 +11,21 @@
 from urllib3.util.retry import Retry
 
 
+EARTHDATA_LOGIN_DOMAIN = 'urs.earthdata.nasa.gov'
+
+
+def write_credentials_to_netrc_file(
+    username: str, password: str, domain: str = EARTHDATA_LOGIN_DOMAIN, append: bool = False
+):
+    """Write credentials to .netrc file"""
+    netrc_file = Path.home() / '.netrc'
+    if netrc_file.exists() and not append:
+        logging.warning(f'Using existing .netrc file: {netrc_file}')
+    else:
+        with open(netrc_file, 'a') as f:
+            f.write(f'machine {domain} login {username} password {password}\n')
+
+
 def _get_download_path(url: str, content_disposition: str | None = None, directory: Path | str = '.'):
     filename = None
     if content_disposition is not None: