The aircraft was designed in response to a Polish Air Force requirement of 1946 for a trainer to replace the Soviet UT-2, which was obsolete.

The entire design was Polish, except for the engine, which was a license-built Soviet radial, the Shvetsov M-11D (93 kW, 125 hp).

After tests, an improved variant, the Junak 2 was flown on July 12, 1949. Notable changes from the Junak 1 included the cockpit being moved forward, the fin being increased in area, a more powerful M-11FR engine (118 kW, 160 hp) was fitted and the massive landing gear covers were deleted.

Tadeusz Sołtyk, then working in the Aviation Institute (Instytut Lotnictwa - IL) in Warsaw, proposed a Junak development with a bubble canopy, retractable landing gear and other improvements, designated the TS-7 Chwat, but it was not ordered by the authorities and remained on the drawing board.

Instead, when the Polish Air Force was equipped with its first jet fighters, (the Yak-23 and MiG-15), there appeared to be a need for a trainer with a tricycle landing gear.

The Junak was the first aircraft mass-produced in Poland after World War II, the Polish aviation industry having been annihilated.

On the other hand, it was considered a difficult aircraft to learn to fly, because a student in a rear cockpit had worse view.

It had two-spar wings of wooden construction and a trapezoidal shape; they were covered with canvas and plywood and were fitted with split flaps.

In 1963 a group of 12 African pilot trainees from Algeria, Togo and Angola were taught to fly at Krosno, Poland, and they flew Junak 3.