In April and May 1947 she participated in 8th Fleet exercises, and cruised with the United States Naval Academy and NROTC midshipmen to northern European ports during June and July.

Returning to the United States, she exercised in the Norfolk area until September when she weighed anchor to take part in Operation "Sunec" with calls at Greenland, Labrador, and Newfoundland.

In 1956 Fort Mandan conducted amphibious training exercises at Vieques, Puerto Rico, and underwent overhaul at Baltimore before steaming again for the far north where she cruised in September and October.

From September through November 1957 she was attached to MSTS for Arctic Service, successfully transporting Army men and equipment from Greenland to Newfoundland and Virginia in a winter closing-out operation.

On 3 July, while visiting the French port of Sète, Fort Mandan sailors assisted local firefighters in extinguishing a fire on the Italian gasoline tanker Ombrina.