diff --git a/analytics/tests/conftest.py b/analytics/tests/conftest.py
index 3c696a2f6..8f58fe107 100644
--- a/analytics/tests/conftest.py
+++ b/analytics/tests/conftest.py
@@ -287,6 +287,12 @@ def reset_aws_env_vars(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setenv("AWS_DEFAULT_REGION", "us-east-1")
 
 
+@pytest.fixture(autouse=True)
+def use_cdn(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Set up CDN URL environment variable for tests."""
+    monkeypatch.setenv("CDN_URL", "http://localhost:4566")
+
+
 @pytest.fixture
 def mock_s3() -> boto3.resource:
     """Instantiate an S3 bucket resource."""
diff --git a/api/local.env b/api/local.env
index 0ac1aa68f..7867cc68b 100644
--- a/api/local.env
+++ b/api/local.env
@@ -150,3 +150,5 @@ DEPLOY_GITHUB_REF=main
 DEPLOY_GITHUB_SHA=ffaca647223e0b6e54344122eefa73401f5ec131
 DEPLOY_TIMESTAMP=2024-12-02T21:25:18Z
 DEPLOY_WHOAMI=local-developer
+
+CDN_URL=http://localhost:4566/local-mock-public-bucket
diff --git a/api/src/services/opportunities_v1/get_opportunity.py b/api/src/services/opportunities_v1/get_opportunity.py
index d11e18dce..4eae805f6 100644
--- a/api/src/services/opportunities_v1/get_opportunity.py
+++ b/api/src/services/opportunities_v1/get_opportunity.py
@@ -5,10 +5,17 @@
 
 import src.adapters.db as db
 import src.util.datetime_util as datetime_util
+from src.adapters.aws import S3Config
 from src.api.route_utils import raise_flask_error
 from src.db.models.agency_models import Agency
 from src.db.models.opportunity_models import Opportunity, OpportunityAttachment, OpportunitySummary
-from src.util.file_util import pre_sign_file_location
+from src.util.env_config import PydanticBaseEnvConfig
+from src.util.file_util import convert_public_s3_to_cdn_url, pre_sign_file_location
+
+
+class AttachmentConfig(PydanticBaseEnvConfig):
+    # If the CDN URL is set, we'll use it instead of pre-signing the file locations
+    cdn_url: str | None = None
 
 
 def _fetch_opportunity(
@@ -50,7 +57,15 @@ def get_opportunity(db_session: db.Session, opportunity_id: int) -> Opportunity:
         db_session, opportunity_id, load_all_opportunity_summaries=False
     )
 
-    pre_sign_opportunity_file_location(opportunity.opportunity_attachments)
+    attachment_config = AttachmentConfig()
+    if attachment_config.cdn_url is not None:
+        s3_config = S3Config()
+        for opp_att in opportunity.opportunity_attachments:
+            opp_att.download_path = convert_public_s3_to_cdn_url(  # type: ignore
+                opp_att.file_location, attachment_config.cdn_url, s3_config
+            )
+    else:
+        pre_sign_opportunity_file_location(opportunity.opportunity_attachments)
 
     return opportunity
 
diff --git a/api/src/util/file_util.py b/api/src/util/file_util.py
index 3322c3c5b..bd499e445 100644
--- a/api/src/util/file_util.py
+++ b/api/src/util/file_util.py
@@ -166,3 +166,16 @@ def read_file(path: str | Path, mode: str = "r", encoding: str | None = None) ->
     """Simple function for just getting all of the contents of a file"""
     with open_stream(path, mode, encoding) as input_file:
         return input_file.read()
+
+
+def convert_public_s3_to_cdn_url(file_path: str, cdn_url: str, s3_config: S3Config) -> str:
+    """
+    Convert an S3 URL to a CDN URL
+
+    Example:
+        s3://bucket-name/path/to/file.txt -> https://cdn.example.com/path/to/file.txt
+    """
+    if not is_s3_path(file_path):
+        raise ValueError(f"Expected s3:// path, got: {file_path}")
+
+    return file_path.replace(s3_config.public_files_bucket_path, cdn_url)
diff --git a/api/tests/src/api/opportunities_v1/test_opportunity_route_get.py b/api/tests/src/api/opportunities_v1/test_opportunity_route_get.py
index 722e6df35..3d53d5d4c 100644
--- a/api/tests/src/api/opportunities_v1/test_opportunity_route_get.py
+++ b/api/tests/src/api/opportunities_v1/test_opportunity_route_get.py
@@ -109,8 +109,9 @@ def test_get_opportunity_with_agency_200(client, api_auth_token, enable_factory_
 
 
 def test_get_opportunity_s3_endpoint_url_200(
-    client, api_auth_token, enable_factory_create, db_session, mock_s3_bucket
+    client, api_auth_token, enable_factory_create, db_session, mock_s3_bucket, monkeypatch_session
 ):
+    monkeypatch_session.delenv("CDN_URL")
     # Create an opportunity with a specific attachment
     opportunity = OpportunityFactory.create(opportunity_attachments=[])
     object_name = "test_file_1.txt"
@@ -153,3 +154,34 @@ def test_get_opportunity_404_not_found_is_draft(client, api_auth_token, enable_f
         resp.get_json()["message"]
         == f"Could not find Opportunity with ID {opportunity.opportunity_id}"
     )
+
+
+def test_get_opportunity_returns_cdn_urls(
+    client, api_auth_token, monkeypatch_session, enable_factory_create, db_session, mock_s3_bucket
+):
+    monkeypatch_session.setenv("CDN_URL", "https://cdn.example.com")
+    """Test that S3 file locations are converted to CDN URLs in the response"""
+    # Create an opportunity with a specific attachment
+    opportunity = OpportunityFactory.create(opportunity_attachments=[])
+
+    object_name = "test_file_1.txt"
+    file_loc = f"s3://{mock_s3_bucket}/{object_name}"
+    OpportunityAttachmentFactory.create(
+        file_location=file_loc, opportunity=opportunity, file_contents="Hello, world"
+    )
+
+    # Make the GET request
+    resp = client.get(
+        f"/v1/opportunities/{opportunity.opportunity_id}", headers={"X-Auth": api_auth_token}
+    )
+
+    # Check the response
+    assert resp.status_code == 200
+    response_data = resp.get_json()["data"]
+
+    # Verify attachment URL is a CDN URL
+    assert len(response_data["attachments"]) == 1
+    attachment = response_data["attachments"][0]
+
+    assert attachment["download_path"].startswith("https://cdn.")
+    assert "s3://" not in attachment["download_path"]
diff --git a/api/tests/src/util/test_file_util.py b/api/tests/src/util/test_file_util.py
index 06cddbf0c..30eac915c 100644
--- a/api/tests/src/util/test_file_util.py
+++ b/api/tests/src/util/test_file_util.py
@@ -211,3 +211,35 @@ def test_move_file_local_disk(tmp_path):
     assert file_util.file_exists(other_file_path) is True
 
     assert file_util.read_file(other_file_path) == contents
+
+
+@pytest.mark.parametrize(
+    "s3_path,cdn_url,expected",
+    [
+        (
+            "s3://local-mock-public-bucket/path/to/file.pdf",
+            "https://cdn.example.com",
+            "https://cdn.example.com/path/to/file.pdf",
+        ),
+        (
+            "s3://local-mock-public-bucket/opportunities/9/attachments/79853231/manager.webm",
+            "https://cdn.example.com",
+            "https://cdn.example.com/opportunities/9/attachments/79853231/manager.webm",
+        ),
+        # Test with subdirectory in CDN URL
+        (
+            "s3://local-mock-public-bucket/file.txt",
+            "https://cdn.example.com/assets",
+            "https://cdn.example.com/assets/file.txt",
+        ),
+    ],
+)
+def test_convert_s3_to_cdn_url(s3_path, cdn_url, expected, s3_config):
+    assert file_util.convert_public_s3_to_cdn_url(s3_path, cdn_url, s3_config) == expected
+
+
+def test_convert_s3_to_cdn_url_invalid_path(s3_config):
+    with pytest.raises(ValueError, match="Expected s3:// path"):
+        file_util.convert_public_s3_to_cdn_url(
+            "http://not-s3/file.txt", "cdn.example.com", s3_config
+        )