[2] The first departure was Nemanja Milunović who left the club after his two and a half season contract signed in December 2018 expired.

[3] On 7 June 2021 Željko Gavrić, who is a product of club's academy, made his international debut for Serbia national football team in a friendly match against Jamaica.

He arrived in Red Star in summer of 2017 and spent previous season on loan at Portuguese side Famalicão.

Club also announced that four young players were recalled from their loans and added to the first squad for the summer training camp: Lazetić, Matić and Nikola Stanković from Grafičar and Gordić from Mačva Šabac.

[9] On 1 July 2021 Red Star brought back Nenad Krstičić from Greek side AEK Athens.

[11] On 3 July 2021 club announced that they signed three-years contract with Norwegian international forward Ohi Omoijuanfo.

He arrived on one-year loan from Ligue 1 side Angers SCO with 1.2 million euros buyout option.

[15] Serbian SuperLiga started on 16 July with home game against Vojvodina which ended in goalless draw with newcomer Dragović making a debut.

[16][17] Red Star started their European season on 21 July 2021 in second qualifying round of UEFA Champions League.

[26] Red Star won 6–2 on aggregate and qualified for the Europa League group stage for a second consecutive season.

[28] In the first match Comorian forward Ben scored his 14th goal for the Red Star in international competitions making him top foreign scorer in the history of the club and fifth overall.

[32] On 30 August 2021 Serbian defender Srđan Babić was loaned to the Segunda División side Almería with a buy out option at the end of the season.

Former Netherlands under-21 international player arrived from Chinese side Changchun Yatai and signed three-years contract.

Besides those four players Ben made two more caps for Comores in friendly games scoring a hat-trick in one of them, Miloš Gordić, Strahinja Eraković, Nikola Stanković and Marko Lazetić represented Serbian youth teams and Richard Odada who plays on a loan at Metalac made his international debut for Kenya.

In the first of them, 3–0 victory against Proleter on 11 September, Richairo Živković made his debut for the club coming in as a half time substitution.

[38] Club started group stage of the Europa League with a 2–1 home game win against Portuguese side Braga.

Club was scheduled to start this season of Serbian Cup in the round of 32 on 27 October, but that match was rescheduled to a 18 November.

Milan Borjan played two games for Canada in CONCACAF 2022 FIFA World Cup qualification conceding one goal.

Finally Miloš Gordić, Strahinja Eraković and Petar Stanić received call-up for Serbia national under-21 football team for their 2023 European Under-21 Championship qualification.

With one game remaining in December Red Star secured European spring for two consecuive seasons and last group stage match in December (away game against Braga) will determine whether it will continue its run in Europe League or be transferred into 2021–22 UEFA Europa Conference League.

Red Star won all three of them with outstanding performance from Aleksandar Katai who scored club's first hat-trick of the season in an away game against Mladost.

[53] Other notable performance was by Ben in a home game against Spartak in which he scored 2 goals and 1 assist also earning the title of the Superliga's Player of the Week.

Milan Borjan also received international callup for Canada in third Round of CONCACAF's 2022 FIFA World Cup qualifications.

Mustapha, who arrived at the club in January 2020, spent previous season and a half on loans at Zlatibor Čajetina and Radnički Sremska Mitrovica.

[69] On 27 January club sold young forward Marko Lazetić to Italian powerhouse Milan for an estimated fee of €4 million.

[70] On 29 January club sold Serbian defensive midfielder to Spanish side Granada for an estimated fee of €1.5 million.

[73] On the same day Ghanaian midfielder Ibrahim Mustapha was loaned out to Serbian SuperLiga side FK Novi Pazar until the end of the season.

Serbian goalkeeper Marko Ćopić, who was on loan at Grafičar Beograd since the start of the season, extended his contract with the club until summer of 2024.

Miloš Gordić, Strahinja Eraković and Andrija Radulović received callups for Serbia U21 selection to play in 2023 UEFA European Under-21 Championship qualifications.

Lastly Nikola Stanković and Nemanja Motika were called up for Serbia U19 selection and both played in a single friendly game.