[1] He was trained under Sir Charles Lanyon before moving to work in Dublin, where he became principal assistant to William George Murray.

In 1865 he became the diocesan architect of the united dioceses of Down, Connor and Dromore in 1865, and from then on Church architecture was Drew's principal activity.

[3] Among other projects, he was responsible for the design of the Ulster Bank on Dame Street, Rathmines Town Hall (completed 1899) and the Graduates' Building at Trinity College.

[1] He was knighted in the 1900 Birthday Honours and was inaugural president of the Royal Society of Ulster Architects, serving from 1901 to 1903.

[1][6] In February 1910, he underwent an operation for appendicitis which left him in a critical condition, and he died on 13 March 1910.