Most Southern trains will be diverted to London Bridge over May weekends.
Services will also be affected two Sundays in June as major signalling upgrades continue on lines into London Victoria.
The investment will modernise 1980s track and signalling, improve reliability on the network and help even more passenger and freight trains arrive at their destinations on time.
This phase of work, to take place between London Victoria, Clapham Junction and Balham, and the West London Lines from Clapham to Shepherds Bush, will continue until after Christmas 2022.
On the following dates, most Southern trains will be diverted to London Bridge and no trains will run between Victoria-East Croydon.
• Saturday 1 to Sunday 3 May (Bank Holiday)
• Saturday 8 to Sunday 9 May
• Saturday 15 to Sunday 16 May
• Saturday 22 to Sunday 23 May
• Saturday 29 to Monday 31 May (Bank Holiday)
• Sunday 6 June
• Sunday 27 June.
Rail tickets will be accepted on London Underground services between London Victoria, London Bridge and Balham, and on London Buses between Balham and Streatham Hill. Tickets will also be valid on South Western Railway services between Clapham Junction and London Waterloo. A limited rail replacement service will operate between East Croydon and Clapham Junction for local journeys.