Originally a product of Barcelona's La Masia, Simons signed for Paris Saint-Germain (PSG) in July 2019, where he would initially join the under-19s before making his professional debut in 2021.

In 2022, Simons returned to his native Netherlands with PSV, winning the KNVB Cup, Johan Cruyff Shield, and Eredivisie top scorer award in his only season at the club.

Initially playing for the Netherlands at youth level, Simons received his first call-up to the national team for the 2022 FIFA World Cup, and made his debut at the tournament.

[9][10] In July 2019, Simons moved to French club Paris Saint-Germain (PSG), having failed to agree a new contract with Barcelona.

[12][13] On 10 February 2021, Simons made his professional debut for PSG, coming on as a substitute for Julian Draxler in a 1–0 Coupe de France win over Caen.

[19] He eventually made his first appearance of the season for PSG in a 3–0 cup win over Feignies Aulnoye on 19 December, his first ever professional start.

[29][30] Simons scored his first career goal on his PSV debut, a 5–3 win over rivals Ajax in the Johan Cruyff Shield on 30 July 2022.

[38] Simons finished the club season with twenty-two goals and twelve assists in forty-eight games across all competitions, and won two Player of the Month awards in August 2022 and March 2023.

[39][40] On 16 July 2023, it was announced by PSV that Simons had departed the club's training camp in order to finalize a transfer back to Paris Saint-Germain.

[42][43] Immediately after being signed back by Paris Saint-Germain, Simons was loaned out to Bundesliga club RB Leipzig for the 2023–24 season.

[49] In the second fixture against Red Star Belgrade on 7 November, Simons scored the opening goal in a 2–1 win, securing qualification to the round of 16.

[58] On 11 November, he was officially called up for the 2022 FIFA World Cup in Qatar by head coach Louis van Gaal.

[66] In June 2023, Simons was a member of the Dutch squad for the 2023 UEFA Nations League Finals, starting against both Croatia in the semi-final and Italy in the third place play-off.

[72][73] In August 2018, he featured in a Nike commercial titled "Awaken the Phantom" alongside players Philippe Coutinho, Kevin De Bruyne, Neymar, Ronaldinho, Pierre-Emerick Aubameyang, and Andrea Pirlo.