The station was opened on 6 March 1865 when services began on the Bristol Port Railway and Pier (BPRP), a self-contained railway which ran along the north bank of the River Avon to a deep water pier on the Severn Estuary at Avonmouth. The route was standard gauge single track, with Sea Mills initially the first station along the line, from the southern terminus at . A single -long uncovered platform was provided on the north side of the line, with a wooden building containing the booking office and porter's office. The station staff consisted of a stationmaster with a porter being brought in from Hotwells when needed. A south-facing goods siding was provided, but the station mostly dealt with passengers and parcels. The initial service was six trains per day in each direction.