The Mid-Kent line is the successor to railways built by the Mid Kent Railway between 1857 and 1882. The Railway was originally planned to carry traffic through mid Kent, but in the event, because other railways were being built at the time (notably the line constructed by the London, Chatham and Dover Railway via Penge East), the scheme did not materialise. The South Eastern Railway worked the line.

The line was opened on 1 January 1857 between Lewisham, now in the London borough of that name, and Beckenham Junction. Stations on that section are:

• Ladywell
• Catford Bridge
• Lower Sydenham - station rebuilt and moved in 1907
• New Beckenham - this station became a junction when the West End of London & Crystal Palace Railway opened its line between Norwood Junction and St Mary Cray

In 1864 the line was extended to Addiscombe, near Croydon and in 1882 the Hayes branch was opened. Today trains run only to Hayes: Tramlink now occupies the track of the former main line.