Wimbledon's population continued to grow at the start of the 20th century, a condition recognised in 1905 when the urban district was incorporated as the Municipal Borough of Wimbledon, with the power to select a Mayor.
By the end of the first decade of the new century Wimbledon had established the beginnings of the Wimbledon School of Art at the Gladstone Road Technical Institute and acquired its first cinema and the theatre. Somewhat unusually, at its opening the theatre's facilities included a Turkish baths .
In 1931, the council built itself a new red brick and Portland stone Town Hall next to the station on the corner of Queen's Road and Wimbledon Bridge. The architects were Bradshaw Gass & Hope.
By the 1930s, residential expansion had peaked in Wimbledon and the new focus for local growth had moved to neighbouring Morden which had remained rural until the arrival of the Underground at Morden station in 1926. Wimbledon station was rebuilt by Southern Railway with a simple Portland stone facade for the opening of a new railway branch line from Wimbledon to Sutton. The Wimbledon to Sutton line opened in 1930.
Damage to housing stock in Wimbledon and other parts of London during the Second World War led to the final major building phase when many of the earlier Victorian houses built with large grounds in Wimbledon Park were sub-divided into apartments or demolished and replaced with apartment blocks. Other parts of Wimbledon Park which had previously escaped being built upon saw local authority estates constructed by the borough council to house some of those who had lost their homes.