1.FSV Mainz 05 (Bundesliga): every transfer in and out, fees paid and earned, squad market value, €157m spent and €245m earned.
| Date | Player | From | To | Fee |
|---|---|---|---|---|
| 2026-07-01 | Tom Krauß | Mainz | 1.FC Köln | €3.5m |
| 2026-07-01 | Sota Kawasaki | Kyoto Sanga | Mainz | €1m |
| 2026-07-01 | Sheraldo Becker | CA Osasuna | Mainz | €500k |
| 2026-07-01 | Ransford Königsdörffer | Hamburg | Mainz | Free |
| 2026-07-01 | Nikolas Veratschnig | Mainz | Salzburg | €3.5m |
| 2026-07-01 | Niklas Tauer | Mainz | Without Club | — |
| 2026-07-01 | Maxim Leitsch | Mainz | Without Club | — |
| 2026-07-01 | Kasey Bos | Mainz | Excelsior | Loan |
| 2026-07-01 | Eric Martel | 1.FC Köln | Mainz | Free |
| 2026-07-01 | Daniel Batz | Mainz | Mönchengladbach | Free |
| 2026-02-02 | Sheraldo Becker | CA Osasuna | Mainz | Loan |
| 2026-02-02 | Arnaud Nordin | Mainz | Stade Rennais | Loan |
| 2026-01-22 | Stefan Posch | Como | Mainz | Loan |
| 2026-01-14 | Konstantin Schopp | Mainz | TSV Hartberg | Loan |
| 2026-01-14 | Hyun-seok Hong | Mainz | KAA Gent | Loan |
| 2026-01-06 | Silas | Stuttgart | Mainz | €150k |
| 2026-01-02 | Phillip Tietz | Augsburg | Mainz | €4m |
| 2026-01-01 | Kacper Potulski | FSV Mainz 05 II | Mainz | — |
| 2025-09-01 | William Bøving | Sturm Graz | Mainz | €3.5m |
| 2025-07-31 | Marco Richter | Mainz | Darmstadt 98 | Loan |