| Club: | Arminia Bielefeld |
| Season: | 2020–21 |
| Chrtitle: | President |
| Chairman: | Hans-Jürgen Laufer |
| Mgrtitle: | Head coach |
| Manager: | Uwe Neuhaus (until 1 March) Frank Kramer (from 2 March) |
| Stadium: | Bielefelder Alm |
| League: | Bundesliga |
| League Result: | 15th |
| Cup1: | DFB-Pokal |
| Cup1 Result: | First round |
| League Topscorer: | Ritsu Dōan Fabian Klos (5 each) |
| Season Topscorer: | Ritsu Dōan Fabian Klos (5 each) |
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| Prevseason: | 2019–20 |
| Nextseason: | 2021–22 |
The 2020–21 Arminia Bielefeld season was the club's 116th season in existence and the first season back in the top flight of German football. In addition to the domestic league, Arminia Bielefeld participated in this season's edition of the DFB-Pokal. The season covered the period from 1 July 2020 to 30 June 2021.
Arminia was the team with the lowest budget in the Bundesliga. After a defeat in the first round of the DFB-Pokal they had a quite promising start in the Bundesliga season, but from the 4th matchday onwards they could be found among the last five teams in the league table, from the 6th matchday onwards amongst the last four teams. In March, the manager Uwe Neuhaus was replaced by Frank Kramer. A 2–0 win over VfB Stuttgart on the final matchday secured the 15th rank and thus their spot in the 2021–22 Bundesliga.
| Date | Pos. | Name | From | Type | |
|---|---|---|---|---|---|
| 30 June 2020 | MF | Can Özkan | Alemannia Aachen | End of Loan | |
| 30 June 2020 | GK | Nikolai Rehnen | Alemannia Aachen | ||
| 5 July 2020 | FW | Prince Osei Owusu | 1860 Munich | ||
| 17 August 2020 | FW | Sergio Córdova | FC Augsburg | Loan | [2] |
| 5 September 2020 | MF | Ritsu Dōan | PSV Eindhoven | [3] | |
| 5 October 2020 | MF | [4] | |||
| 1 July 2020 | DF | Jacob Barrett Laursen | OB | Free Transfer | [5] |
| 15 July 2020 | FW | Christian Gebauer | SCR Altach | ||
| 15 July 2020 | DF | Nathan de Medina | Mouscron | ||
| 15 July 2020 | FW | Noel Niemann | 1860 Munich | [6] | |
| 4 September 2020 | DF | Mike van der Hoorn | Swansea City | [7] |
| Date | Pos. | Name | To | Type | Transfer Fee | ||
|---|---|---|---|---|---|---|---|
| 30 June 2020 | GK |  Ágoston Kiss | Szombathelyi Haladás | End of Loan | Free | ||
| 1 July 2020 | FW | Nils Quaschner | Retired | – | – | ||
| 1 July 2020 | MF | Tom Schütz | – | End of Contract | – | ||
| 1 July 2020 | DF | Jonathan Clauss | RC Lens | Free Transfer | Free | [8] | |
| 4 August 2020 | DF | Florian Hartherz | Fortuna Düsseldorf | Free Transfer | Free | ||
| 7 August 2020 | MF | Free Transfer | Free | [9] | |||
| 9 August 2020 | MF | Keanu Staude | Würzburger Kickers | Free Transfer | Free | [10] | |
| 12 August 2020 | GK | Philipp Klewin | Erzgebirge Aue | Free Transfer | Free | ||
| 14 August 2020 | DF |  Álex Pérez | UD Logroñés | Free Transfer | Free | [11] | |
| 1 September 2020 | DF | Stephan Salger | 1860 Munich | Free Transfer | Free | [12] | |
| 18 September 2020 | FW | Mervin Kalac | SV Lippstadt | Free Transfer | Free | ||
| 5 October 2020 | FW | Prince Osei Owusu | SC Paderborn | Transfer | |||
| 5 October 2020 | MF | Can Özkan | Næstved BK | Loan | Free | ||
| 1 January 2021 | DF | Brian Behrendt | Eintracht Braunschweig | Transfer | €100K | [13] |
See main article: 2020–21 Bundesliga.
The league fixtures were announced on 7 August 2020.[14]
See main article: 2020–21 DFB-Pokal.
|-! colspan=14 style=background:#dcdcdc; text-align:center| Goalkeepers|-! colspan=14 style=background:#dcdcdc; text-align:center| Defenders|-! colspan=14 style=background:#dcdcdc; text-align:center| Midfielders|-! colspan=14 style=background:#dcdcdc; text-align:center| Forwards|-! colspan=14 style=background:#dcdcdc; text-align:center| Players transferred out during the season
| width=15 | width=15 | width=15 | width=15 | width=165 | Name | width=120 | Bundesliga | width=120 | DFB-Pokal | width=120 | Total | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 8 | MF |  | Ritsu Dōan | 5 | 0 | 5 | ||||||||
| 9 | FW | Fabian Klos | 5 | 0 | 5 | ||||||||||
| 2 | 18 | FW | Sergio Córdova | 2 | 0 | 2 | |||||||||
| 21 | FW | Andreas Voglsammer | 2 | 0 | 2 | ||||||||||
| 2 | 14 | MF |  | Jóan Símun Edmundsson | 1 | 0 | 1 | ||||||||
| 29 | MF |  | Cebio Soukou | 1 | 0 | 1 | |||||||||
| 19 | MF |  | Manuel Prietl | 1 | 0 | 1 | |||||||||
| 10 | MF | Reinhold Yabo | 1 | 0 | 1 | ||||||||||
| 36 | FW | Sven Schipplock | 1 | 0 | 1 | ||||||||||
| 2 | DF | Amos Pieper | 1 | 0 | 1 | ||||||||||
| 7 | MF | | Christian Gebauer | 1 | 0 | 1 | |||||||||
| 11 | MF | | Masaya Okugawa | 1 | 0 | 1 | |||||||||
| 28 | MF | Michel Vlap | 1 | 0 | 1 | ||||||||||
| Own Goal | 3 | 0 | 3 | ||||||||||||
| Totals | 26 | 0 | 26 | ||||||||||||