Mainz U19 (U19 Bundesliga): every transfer in and out, fees paid and earned, squad market value.
| Date | Player | From | To | Fee |
|---|---|---|---|---|
| 2025-07-21 | Player | Mainz U19 | Schott Mainz | Free |
| 2025-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2025-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2025-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2025-07-01 | Kacper Potulski | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2025-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2025-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2025-07-01 | Player | Mainz U19 | Köln II | Free |
| 2025-01-01 | Player | Mainz U19 | Rot-Weiß Walldorf U19 | Free |
| 2024-08-19 | Noa Kljajic | Mainz U19 | Reggiana | Free |
| 2024-07-01 | Kacper Potulski | Mainz 05 U17 | Mainz U19 | Free |
| 2024-07-01 | Player | Mainz U19 | Schweinfurt | Free |
| 2024-07-01 | Player | Mainz U19 | Darmstadt 98 U19 | Free |
| 2024-07-01 | Maxim Dal | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2024-07-01 | Player | Mainz U19 | Jahn Regensburg U19 | Free |
| 2024-07-01 | Player | Mainz U19 | Magdeburg U19 | Free |
| 2024-07-01 | Player | Mainz U19 | Hamburger SV II | Free |
| 2024-07-01 | J. Amann | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2024-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |
| 2024-07-01 | Player | Mainz U19 | 1.FSV Mainz 05 | Free |