The Westside Theatre building was designed by architect Henry F. Kilburn as the Second German Baptist Church in 1890. Nearly a century later, the space housed a discotheque, Club Sanctuary, until it finally was converted into two theatres (upstairs and downstairs) in 1973.

The Chelsea Theatre Group presented the first production – David Storey’s The Contractor – in October 1973. The building was renamed the Chelsea Westside Theatre. Under the management of Raymond L. Gaspard, the theatre was re-christened the Westside Arts Theatre from 1981 until 1990.

After an extensive renovation by new management, the venue re-opened in March 1991 as the Westside Theatre. The Upstairs Theatre has a capacity of 270 seats, while the Downstairs Theatre holds 249 seats.