Kaczmarek moved from Poland to Germany at the age of 9 and only played on amateur level as an active footballer. He started his coaching career in 2009 as a part of the coaching staff at
Bonner SC. From January 2011, he took charge of the U19's at the club and later a half year for the first team, which he was in charge of until the end of 2011, where he was hired as assistant manager for the
Egyptian national team under manager
Bob Bradley. Bradley and his coaching staff, including Kaczmarek, left in November 2013. On 30 March 2014, Kaczmarek followed Bradley to Norwegian club
Stabæk IF, still as his assistant. On 8 January 2020, Kaczmarek was appointed assistant coach of head coach
Kosta Runjaić at
Pogoń Szczecin. On 1 September 2021, he was announced as the manager of
Lechia Gdańsk. In his
first season in charge, he led Lechia to a 4th-place finish in
Ekstraklasa. Exactly a year after his appointment, he was relieved of his duties following a poor start to the campaign, with Lechia crashing out of the
UEFA Europa Conference League second qualifying round and at the bottom of the league table, with just one point following six games. On 10 April 2023, Kaczmarek was appointed manager of
Eerste Divisie side
Den Bosch on a two-year contract. He was sacked on 11 April 2024, with a record of 7 wins, 10 draws and 23 losses across all competitions. On 11 June 2024, he joined
NAC Breda's coaching staff as an assistant under manager
Carl Hoefkens. ==Honours==