Mimbelli was a commander of a Torpedo boat destroyer flotilla which fought in the Battle of Crete he was responsible for defending a convoy of two thousand Germans going to Crete in the face of superior British forces. Although the odds were heavily stacked against them (one torpedo boat against the seven ships of Force D) more than two thirds of the convoy survived due to Mimbelli's maneuvers.
He was also the commander of the Italian naval force based in the Black Sea, where he commanded a force of MAS boats. The Italian flotilla was responsible for sinking two submarines and a transport ship. They also torpedoed the Soviet cruiser Molotov which was not repaired until after the end of the conflict.
In 1946 Mimbelli was appointed captain of the Cruiser Giuseppe Garibaldi. He was subsequently promoted to Rear Admiral and became commander of the Italian Naval Academy. He retired as a Vice Admiral in 1964.