Developed from the earlier Ka-15 to meet a 1958 Soviet Navy requirement for a heavy shipborne helicopter. The Ka-20 had a similar twin contra-rotating, three-blade rotors of the earlier Ka-15 design and was powered by two 670 kW turboshaft engines. The Ka-20 was built to demonstrate the feasibility of mounting the turbo-shaft engines above the cabin and it had no mission equipment or corrosion protection although it was fitted with a nose mounted radome.
The Ka-20 first became known outside of the Soviet Union at the 1961 Tushino Aviation Day display where a Ka-20 was demonstrated fitted with dummy missiles on the cabin sides. The design was developed as the Ka-25 anti-submarine helicopter.