In 1983–84 Lechia were again in the second tier (west group), and qualified for the Polish SuperCup () due to winning the Polish Cup the season before. It was the first-ever season of the Super Cup, and saw the cup winning team play the Ekstraklasa champions, resulting in Lechia playing Lech Poznań. Despite Lech being heavy favourites Lechia won the super cup with a late goal from Jerzy Kruszczyński. This resulted in 1983 being the most successful season in the club's history up to that point, with the team winning both cup competitions it participated in despite not being in the top division. Lechia's stay out of the Ekstraklasa wasn't to last long, however, with the team winning the 1983–84 II Liga season, and as a result were promoted back to the Ekstraklasa. A division they had narrowly missed out of playing in many seasons before, and was their first time back in the top tier for 21 seasons. That season Lechia also qualified for the UEFA Cup Winners' Cup due to winning the Polish Cup the season before. In the first round, Lechia was drawn to Italian footballing giants, Juventus. The first game was played in Turin, Italy, with Juventus easily winning 7–0. With the team knowing they were all but knocked out already the team put on an inspiring performance scoring 2 goals against the European giants in the home leg of the competition. The Lechia home game against Juventus was not only a sporting spectacle, but proved to be a place of mass demonstration for the "Solidarity" movement, which many fans were part of. In the 40,000 crowd was Lech Wałęsa, with the crowds chants of ""Solidarność! Solidarność! Solidarność!"" causing the second half to be delayed by 6 minutes and with broadcasters resulting to mute the whole second half of the TVs broadcast. The Lechia manager, Jerzy Jastrzębowski, said of the event; "We were in the dressing room during half-time when we heard it and it sent shivers down our spines, the whole ground singing 'Solidarnosc'."