Boro U21 (): every transfer in and out, fees paid and earned, and the market value of the squad. €100k spent, €1.2m earned. Record complete to 2025-07-01.
| Date | Player | From | To | Fee |
|---|---|---|---|---|
| 2025-07-01 | Zach Hemming | Boro U21 | Chesterfield | — |
| 2025-01-03 | Zach Hemming | Boro U21 | St. Mirren | Loan |
| 2024-07-23 | Zach Hemming | Boro U21 | Leyton Orient | Loan |
| 2023-07-01 | Zach Hemming | Boro U21 | St. Mirren | Loan |
| 2022-08-01 | Rumarn Burrell | Boro U21 | Falkirk | Free |
| 2022-07-01 | Zach Hemming | Boro U21 | Kilmarnock FC | Loan |
| 2021-07-30 | Rumarn Burrell | Boro U23 | Kilmarnock FC | Loan |
| 2021-07-01 | Zach Hemming | Boro U23 | Kilmarnock FC | Loan |
| 2021-02-03 | Malik Dijksteel | Telstar U21 | Boro U23 | Free |
| 2021-01-14 | Rumarn Burrell | Boro U23 | Bradford | Loan |
| 2020-08-22 | Enes Mahmutovic | Boro U23 | PFC Lviv | Free |
| 2020-01-01 | Djed Spence | Boro U23 | Middlesbrough | — |
| 2019-11-23 | Zach Hemming | Boro U23 | Blyth Spartans | Loan |
| 2019-08-22 | Zach Hemming | Boro U23 | Hartlepool | Loan |
| 2019-07-24 | Billal Brahimi | Boro U23 | Stade Reims B | €200k |
| 2019-07-01 | Rumarn Burrell | Grimsby U18 | Boro U23 | €100k |
| 2019-07-01 | Enes Mahmutovic | Boro U23 | MVV Maastricht | Loan |
| 2019-07-01 | Nathan Wood | Boro U23 | Middlesbrough | — |
| 2018-10-30 | Zach Hemming | Boro U23 | Darlington | Loan |
| 2018-08-30 | Enes Mahmutovic | Boro U23 | Yeovil Town | Loan |