Delfin displaced 113 tons surfaced and 126 tons submerged. She was 19.6 metres (64 ft) long with a beam of 3.3 metres (11 ft) and a draught of 2.9 metres (9 ft 6 in). The submarine was powered by one gasoline/electric motor that created 300 bhp and 120 hp respectively that drove one shaft. This gave Delfin a speed of 9 knots (17 km/h; 10 mph) surfaced and 4.5 knots (8.3 km/h; 5.2 mph) submerged. The ship was crewed by 22 men, including officers.

