Hemsworth Road is currently closed up to the junction with Warminster Road in Norton Lees, causing the 18 and 20 bus services to be diverted.
The reason for the closure is not yet known.
A spokesman for Travel South Yorkshire said: "Service 18 and 20, due to the unannounced road closure of Hemsworth road with the junction of Warminster, are currently on diversion.
"20 will serve a one way loop up Derbyshire ln, Norton Lees Rd, Norton Lees Ln, Scarsdale Rd, Chesterfield Rd, Norton roundabout, Bochum Pkway, Norton Ln then normal route to Hemsworth.
"20 to Ecclesfield will be going straight down Woodseats Road, Chesterfield Road then picking up normal route from Heeley.