[1] Kowalewski made his top-flight debut with Wigry Suwałki during the 1996–97 season, but it was not until 2001–02, after a loan spell with second division side Dyskobolia Grodzisk, that he finally established himself with Legia.

[4] Kowalewski has a reputation of being an excellent penalty-saver, once breaking FC Torpedo Moskva's Vladimir Leonchenko's streak of 13 successful spot-kicks.

Kowalewski replaced Tomasz Kuszczak in Poland's Euro 2008 squad following the Manchester United goalkeeper's back injury.

[7] He had to re-use the UEFA ID card of his team-mate Mariusz Lewandowski to enter the stadium in Klagenfurt for the match against Germany as he did not obtain an accreditation pass due to an oversight by the Polish delegation.

He was the starter against the Czechs as Poland slipped to a 2–0 defeat on 10 October 2009 which killed off any lingering hopes of qualifying for the tournament finals.