Football Club Seoul (K League 1): every transfer in and out, fees paid and earned, squad market value, €2.1m spent and €3.6m earned.
| Date | Player | From | To | Fee |
|---|---|---|---|---|
| 2026-01-27 | Lucas Silva | FC Seoul | EC Vitória | Loan |
| 2026-01-23 | Juan Antonio Ros | TJ Jinmen Tiger | FC Seoul | Free |
| 2026-01-21 | Min-kyu Song | Jeonbuk Hyundai | FC Seoul | Free |
| 2026-01-16 | Sung-yun Gu | Seoul E-Land | FC Seoul | — |
| 2026-01-16 | Seung-beom Son | FC Seoul | Pohang Steelers | — |
| 2026-01-16 | Pil-gwan Ko | FC Seoul U18 | FC Seoul | — |
| 2026-01-16 | Leonardo Ruiz | Seongnam FC | FC Seoul | Free |
| 2026-01-16 | Jeong-beom Son | FC Seoul U18 | FC Seoul | — |
| 2026-01-16 | Hrvoje Babec | NK Osijek | FC Seoul | — |
| 2026-01-16 | Han-min Jung | FC Seoul | Pohang Steelers | Free |
| 2025-11-17 | Ju-hyeok Kang | FC Seoul | Gimcheon Sangmu | Loan |
| 2025-07-31 | Ju-sung Kim | FC Seoul | Sanf. Hiroshima | €1.1m |
| 2025-07-24 | Tae-wook Jeong | Jeonbuk Hyundai | FC Seoul | Loan |
| 2025-07-24 | Shin-jin Kim | FC Seoul | Gangwon FC | — |
| 2025-07-24 | Seong-hoon Cheon | Daejeon Hana C. | FC Seoul | — |
| 2025-07-07 | Anderson Oliveira | Suwon FC | FC Seoul | — |
| 2025-07-03 | Sung-yueng Ki | FC Seoul | Pohang Steelers | — |
| 2025-06-20 | Jin-ya Kim | FC Seoul | Daejeon Hana C. | — |
| 2025-06-02 | Patryk Klimala | Slask Wroclaw | FC Seoul | €300k |
| 2025-04-07 | Jong-beom Baek | FC Seoul | Gimcheon Sangmu | Loan |