Malachy Costello studied painting at the Crawford College of Art, Cork and the Institute of Technology Sligo. Exhibiting since 1983 he has held many solo shows and has participated in many group exhibitions including the Irish Exhibition of Living Art, Eigse, Carlow and others over the years.

His works are in the public collections of the OPW, Bank of America,Co.Councils of counties Roscommon and Sligo, and other corporate bodies, as well as many private collections at home and abroad.