| Serco Circle Business Limited | Private company limited by shares | Live |
| SERCO Consultants Limited | Private company limited by shares | Live |
| SERCO 3 DESIGN COMMUNICATIONS LIMITED | Private company limited by shares | Dissolved |
| SERCO FUNDS LIMITED | Private company limited by shares | Dissolved |
| SERCO GAMMON MOM LIMITED | Private company limited by shares | Dissolved |
| SERCO GROUP (HK) LIMITED | Private company limited by shares | Live |
| SERCO (HONG KONG) LIMITED | Private company limited by shares | Dissolved |
| SERCO INTERNATIONAL HONG KONG LIMITED | Private company limited by shares | Dissolved |
| SERCO INTERNATIONAL LIMITED | Private company limited by shares | Live |
| SERCO INVESTMENT COMPANY LIMITED | Private company limited by shares | Dissolved |
| SERCO INVESTMENT LIMITED | Private company limited by shares | Dissolved |
| SERCO GAMMON SKANSKA LIMITED | Private company limited by shares | Dissolved |
| SERCOBEST COMPANY LIMITED | Private company limited by shares | Live |
| SERCODON COMPANY LIMITED | Private company limited by shares | Dissolved |
| SERCOFAST COMPANY LIMITED | Private company limited by shares | Live |
| SERCOINFAL LIMITED | Private company limited by shares | Live |
| SERCOJUNE COMPANY LIMITED | Private company limited by shares | Dissolved |
| SERCOLIGHT COMPANY LIMITED | Private company limited by shares | Live |
| SERCOLINK COMPANY LIMITED | Private company limited by shares | Live |
| SERCOMART COMPANY LIMITED | Private company limited by shares | Dissolved |
| SERCON INVESTMENTS LIMITED | Private company limited by shares | Live |
| SERCOQUIN BUSINESS LIMITED | Private company limited by shares | Live |
| SERCORNIC COMPANY LIMITED | Private company limited by shares | Dissolved |
| SERCOTEC LIMITED | Private company limited by shares | Live |
| SERCOWELL SECRETARIAL LIMITED | Private company limited by shares | Dissolved |
| SERCOWICK COMPANY LIMITED | Private company limited by shares | Live |