A licence to build the PA-34-200T was purchased in 1978, when WSK-Mielec started to co-operate with Western manufacturers. The Polish aircraft were to be fitted with PZL-Franklin F6A-350 220 hp (164 kW) engines. The first Mewa, assembled partly from US-delivered parts, flew on July 25, 1979. However, the Polish communist authorities were reluctant to produce civil aircraft of this class as there was no civil aircraft free market in Poland at that time. As a result, the second prototype, built in Poland, was not flown until 1982 and the third M-20 02, being the basis for serial production, on October 10, 1985. In 1988, an air ambulance version M-20 03 was developed, with Teledyne Continental TSIO/LTSIO-360-KB engines.
After 1990 production of the Mewa commenced for the civilian market. Despite the fact that it won the Teraz Polska award in 1993, interest was very limited and only 33 had been built by the end of 1998.