Lech's Swedish striker Mikael Ishak scored the only goal of the match at the Municipal Stadium in the western Polish city of Poznań in the 41st minute as the two sides began their European campaign on Tuesday.
Lech fans during the game at the Municipal Stadium in Poznań on Tuesday night. Photo: PAP/Jakub Kaczmarczyk
Lech will play Qarabag in the second leg next Tuesday, July 12, in Baku.
The winner of the two matches will go on to face Swiss side FC Zürich in the second round of Champions League qualifiers, Polish state news agency PAP has reported.
The loser will be relegated to the lower Europa League.
To qualify for the Champions League group stage, Lech Poznań need to eliminate Qarabag Agdam, FC Zürich and two other rivals.
Lech in May won the Polish premier league championship for the eighth time.