St Andrew's is a large and ambitious church designed by James Brooks F.R.I.B.A. (1825-1901) and consecrated in 1887. The nave was completed in 1897. The building consists of nave, north and south aisles, chancel, shallow transepts and north east and south east chapels. There is a fleche over the crossing containing a single bell.  The construction is of brick with stone facings. The interior is lofty and impressive, 'early English' style. Unusually for a parish church there is a triforium (blind in chancel) above the nave arcading, and lancet clerestory, The east window is a five light lancent with a rose window at the west end. The reredos is 19th century by Nathaniel Westlake, who also painted the fourteen Stations of the Cross on the aisle walls.  There is a set of ten lancet windows in the nave, modern work designed by John Hayward, depicting the life of Christ.

Attached by a short cloister to the south east corner of the church is the Clergy House, also by Brooks. The vestry block was recently remodelled and now provides the entrance to the Parish Centre which was designed by the late Tom Hornsby, architect of Newcastle Cathedral. It is a worthy and useful addition to the whole complex of buildings.

Also by Brooks are the former Parish Institute at the west end, and the former Junior school (now a sixth-form college) on the opposite corner. The Parish School in Belton Road, though mainly rebuilt in the 70's, contains the original mission church & school built when Willesden Green was first being developed in the 1870's.