John Cassidy was born in Slane, Co. Meath, Ireland on 1 January 1860. In 1880 he moved to Dublin where he took night classes at an art school. In 1883 he moved to Manchester and attended Manchester School of Art. During his time at the school he was awarded four National medals and several Queen's prizes. He subsequently remained in Manchester where he lived for the rest of his life. He established a studio, initially in Barton Arcade in the centre of the city, and then, by 1894 in Lincoln Grove, Chorlton-on-Medlock, a suburb of Manchester. In 1887 he began teaching at Manchester School of Art and that year gave demonstrations in modelling from life at the Manchester Royal Jubilee Exhibition. Cassidy exhibited at the Royal Academy in London; the Royal Cambrian Academy on Conwy, Wales; the Walker Art Gallery in Liverpool; Manchester Art Gallery; Leeds City Art Gallery; Royal Birmingham Society of Artists; and at the Royal Hibernian Academy in Dublin.