He is known for portraying pianist and composer Frédéric Chopin in the biographical film Chopin: Desire for Love (2002), Pope John Paul II in the TV miniseries Karol: A Man Who Became Pope (2005) and its sequel Karol: The Pope, The Man (2006), Tomas in the Marvel Cinematic Universe Disney+ series Hawkeye (2021) and Sergei Nikulov in the Apple TV+ original science fiction space drama series For All Mankind (2021–2024).

The movie was viewed by several dozen million viewers, and made him popular in Italy, Latin America and many other Catholic countries.

Adamczyk also managed to take advantage of his popularity abroad to act at the Sala Uno Theatre in Rome, in Italian.

In 2014, Adamczyk, Bartosz Opania and Paweł Domagała starred in the comedy film Wkreceni.

In animated films he voiced, among others, Melman the giraffe in Madagascar, Lightning McQueen in Cars, and Syndrome in The Incredibles.