In 1935, the ship had an aircraft catapult installed, along with cranes to handle float planes. A pole mast was also installed on the rear side of the aft funnel. "Köln" continued to serve as a training ship until early 1936, when she was transferred to fishery protection duty. Later that year, she joined the non-intervention patrols off Spain during the Spanish Civil War. After the German heavy cruiser was attacked by Republican bombers in the so-called ""Deutschland" incident", "Köln" transported wounded crew members from "Deutschland" back to Germany. "Köln" conducted a further four patrols off Spain before returning to fishery protection in the North Sea in 1938. Late in the year, she went into drydock for a refit in Kiel.