MacWhirter was born in Edinburgh where he studied at the Trustees Academy under Robert Scott Lauder and John Ballantyne. He spent long periods sketching and studying outdoors and exhibited his first picture at the Royal Scottish Academy when aged only 14. He was elected an associate member of the Royal Scottish Academy in 1867 and shortly after moved to London where he established a reputation as a fine landscape artist. He travelled widely in Europe and America, the Alps being a great inspiration. He exhibited at the Royal Academy, Grosvenor Gallery and elsewhere. Works by MacWhirter are in many public collections.