Niall graduated from NCAD, Dublin in 1982. He has exhibited since 1980 including RHA annual shows and Aer Rianta. He has had continuous solo exhibitions at the Hallward Gallery, Dublin, and the Mill Cove Gallery, Cork. His work is represented in many important collections, including BP Headquarters in Belgium, Government Buildings, The Arts Council of Ireland, AIB Investment Bank, OPW, Showerings, Clonmel. V.E.C., N.C.V.A. Dublin.

He works from the Irish landscape and has focused his painting on the Wicklow Mountains for the past thirty years. This recent work changes its emphasis from the isolated landscape of Wicklow to an urban setting of remembrance reflecting distinctive winter locations of frost, shadows and light.