Formed in 1920, it was nationalised when the BET Group sold their bus interests to the Transport Holding Company in 1967.
In 1927, the company came to an agreement with the Great Western Railway to take over their bus services in both South Wales, and areas of southern Gloucestershire and northern Somerset surrounding Bristol and Bath.
Although entire UK railway network was nationalised in 1948 when they passed to the British Transport Commission, many bus services remained in private hands.
After BET sold its operations to the government, Western Welsh became part of the National Bus Company.
In 1970, NBC transferred Western Welsh's operations west of Bridgend to its subsidiaries South Wales Transport and Crosville Motor Services.