The station is on the double-track Reading to Basingstoke Line, and comprises two side platforms linked by a footbridge.

The line was promoted by the nominally independent Berks and Hants Railway, but this company was absorbed into the GWR two years before Mortimer station opened.

The approval of the Duke of Wellington, who lived nearby at Stratfield Saye House was required for the station's construction.

BR undertook major renovations of the station buildings in time for the celebrations of the 150th anniversary of the GWR, including removing the 1920s slates and replacing them with orange pantiles in the original style.

[3] Following the privatisation of British Railways, the station is again served by trains running under the Great Western name.