Szymański started training at the age of six at TOP 54 Biała Podlaska. In March 2013, he became a player of Legia Warsaw. In the 2015–16 season, he appeared in 12 matches and scored once for Legia's reserve team. He also played in one UEFA Youth League match and three matches of the Central Junior League, which Legia won after beating Pogoń Szczecin 5–4 on aggregate in a two-legged final, with Szymanski scoring twice in the second leg.[2]
Legia Warsaw
In July 2016, Szymański was promoted to the first team and debuted on the seventh day in a 1–4 loss to Lech Poznań in the Polish Super Cup final.[3] He made his Ekstraklasa debut on 20 August 2016 in a 1–3 loss to Arka Gdynia. In November 2016, he extended his contract with Legia until the end of June 2019. On 3 March 2017, in a 3–1 win over Zagłębie Lubin, he scored his first goal for Legia's first team. In the 2016–17 season, he won the Ekstraklasa title with the club, and was the youngest player to score a league goal that season.[4] He also appeared in nine matches of the third-league reserves, scoring two goals, and five matches of the UEFA Youth League, in which he scored twice. In October 2017, he extended his contract with the club until 2022. In the 2017–18 campaign, he won the Polish Cup with Legia.[5]
Szymański was voted by Dynamo fans as "player of the month" for October 2019.[7] On 9 November 2019, he scored his first goal for Dynamo, the only goal of the game in a 1–0 victory over FC Rubin Kazan. It was the first Dynamo away victory against Rubin in 13 years.[8][9]
On 2 June 2021, he signed a new contract with Dynamo for a five-year term.[10] He was voted player of the month by Dynamo fans for July 2021,[11] August 2021[12] and November 2021.[13]
Feyenoord (loan)
On 22 July 2022, Szymański joined Dutch club Feyenoord on a one-year loan with an option to buy for the club.[14]
On 7 August 2022, he made his Eredivisie debut with Feyenoord against Vitesse and made two assists of 2-5 away win. He scored his first goal for the club on 27 August 2022, scoring the fourth goal in the club's 4–0 win over FC Emmen.[15]
Fenerbahçe
On 12 July 2023, Turkish Süper Lig side Fenerbahçe announced the signing of Szymański on a four-year contract, for €9.75 million.[16][17]
In May 2018, Szymański was named in Poland's preliminary 35-man squad for the 2018 World Cup,[20] but did not make the final 23.[21]
On 9 September 2019, Szymański debuted for the senior Polish squad by replacing Kamil Grosicki in the 70th minute during a UEFA Euro 2020 qualifying match against Austria.[22] He started for the first time in the same qualification on 10 October against Latvia and assisted on one of the goals, resulting in a 3-0 victory for Poland that secured their final tournament spot.[23] Szymański scored his first goal for his country on 19 November 2019 in the last qualifying group game against Slovenia.[24]