The Department of Homeland Security (DHS) manages a diverse warehouse portfolio. According to the Government Accountability Office, managing the Federal government’s real property — which includes warehouses — is a high-risk area. DHS’ components own and lease warehouses for a variety of reasons, such as storing disaster relief supplies, computer equipment, seized assets, and excess property. Our audit objective was to determine the effectiveness of DHS’ process of assessing and managing its warehousing needs. Although DHS has taken steps to assess its warehouses, it cannot effectively manage its warehouse needs because some of the components misclassify many of their warehouses. We found buildings that should not have been on the Department’s warehouse inventory. Conversely, we found buildings that should have been classified as warehouses, but were not. Because the warehouse inventories are inaccurate, DHS cannot manage warehouses or demonstrate compliance with requirements to limit the size of real property inventories and reduce costs. Even though most warehouses we visited were well organized and appeared to support the components’ missions, we identified three warehouses that CBP could potentially consolidate or close and put $1 million per year to better use.