Early into his international career, he helped the Poland national team win the silver medal at the 1992 Summer Olympics.

Almost from the very beginning, he was an automatic first-choice; in his weakest season, his first, he only appeared in 11 Ekstraklasa games, but was crucial in helping oust U.C.

After having started the 1994–95 campaign with Legia (five matches, three goals, another league title), Kowalczyk moved abroad and signed with La Liga side Real Betis, but was never able to reproduce his previous form.

In late 2001 he changed countries again, joining Cyprus' Anorthosis Famagusta FC and netting a career-best 24 goals; after a nearly non-existent second season he finished his professional career in the same country, with APOEL FC, retiring at 32 – afterwards, he would play in amateur football until 2019, with AZS Absolwent UW Warsaw and Weszło Warsaw.

[2] After retiring, Kowalczyk established himself as a football pundit, initially working with Polsat Sport TV.