When the railways were nationalised in 1948, services at Sea Mills came under the aegis of the Western Region of British Railways. Staffing by this point had increased to two porters and two lad porters, managed by the stationmaster at . By 1961 this was reduced to two porters, then to one in 1965. Service levels had decreased slightly by 1955 to 28 towards Avonmouth and 29 towards Bristol, but the services were at regular intervals. Passenger numbers however dropped sharply in 1961 as the result of a fare increase, and so in 1962 a new reduced timetable was enacted, which lost more passengers. A year later in 1963, the Beeching report suggested the complete withdrawal of services along the line, but ultimately only those beyond Severn Beach or via Henbury were withdrawn. From 17 July 1967 all staffing was withdrawn from stations along the line, including Sea Mills, with tickets issued by the train guard. The general reduction in passenger traffic, as well as the transfer of Avonmouth goods traffic to the Henbury Loop Line, allowed the removal of the second track from 19 October 1970, with all services using the original, eastern platform. The station building was sold, and in 2005 was being used by an engineering firm. By 1974, service had reduced to 19 trains per day in each direction.