The church originated in 1900 when an iron mission church was erected on a plot of land in the parish of St Saviour in Markhouse Road, and a separate ecclesiastical parish was created for the church in 1901.

The land for the church was donated by Richard Foster, a wealthy City of London merchant who had supported the building of several other new churches in the area; he also funded the construction of a permanent church building, church hall and vicarage,[1] intended to serve the residents of the new Warner Estate.

[2] The church was built between 1902 and 1903 to the design by W. D. Caröe, in the Arts and Crafts style of Perpendicular Gothic,[2] and was dedicated on 7 November 1903 by Edgar Jacob, the Bishop of St Albans.

A new chapel dedicated to St James was formed in the south aisle of St Barnabas, which included the altar from the former church.

[1] In 1981, the church was given grade II* listed building status.