St John's Church is located just a short walk from the town centre shops (including the Harlequin Shopping Centre), and approximately half a mile from both Watford Junction and High Street main line stations (served by trains from London Euston, Milton Keynes, and Birmingham). Watford Metropolitan tube station is approximately one mile from the church, in West Watford.

There is limited parking at the church, but the Sutton Road public car park (on Estcourt Road) is just a short walk away.

Drivers are advised to access the church via Clarendon Road, turning onto Gartlet Road, then first left into Estcourt Road and first right into Cross Street. There is another vehicular entrance via Queens Road, Loates Lane and Duke Street.