[3] Having started out at local side GKP Gorzów Wielkopolski, Kownacki joined Lech Poznań in 2005, coming through the youth ranks and making it to the first team in December 2013.

He scored his first Ekstraklasa goal in February 2014 in a 5–1 loss at Pogoń Szczecin, becoming one of only five players aged under 17 to have registered in Poland's top flight.

[5] In November, he scored a brace and assisted another goal in Sampdoria's 4–1 Coppa Italia win against Delfino Pescara in the fourth round.

[9] On 22 May 2023, Bundesliga club Werder Bremen announced the signing of Kownacki on a free transfer from Fortuna for the 2023–24 season.

[13] Kownacki was named in Poland's 23-man squad for the 2018 FIFA World Cup in Russia,[14] and was considered back-up to Robert Lewandowski.