Collier was born in 1850, the son of a judge and amateur artist, Lord Monkswell. He was educated at Eton and studied at the Slade School of Art under (Sir) Edward Poynter, in Paris under Jean-Paul Laurens, and in Munich. Although not their pupil, he was encouraged and influenced by Sir Lawrence Alma-Tadema and Sir John Everett Millais. "It was from Millais that he learnt the method, which he has ever since adopted in portraiture, of putting sitter and canvas side by side, looking at them from some distance, and walking backwards and forwards to do the actual painting."
Collier was one of the 24 founding members of the Royal Society of Portrait Painters, of which he became Vice President. He was also a member of the Royal Institute of Oil Painters. He exhibited no fewer than 130 paintings at the Royal Academy and 165 at the Royal Society of Portrait Painters, as well as many others in galleries throughout the country and abroad. He was the author of The Primer of Art (1882), A Manual of Oil Painting (1886) and The Art of Portrait Painting (1905). He was awarded the OBE in 1920. He was the subject of The Art of the Honourable John Collier (1914) by W H Pollock, published by the Art Journal, which lists all his most important subjects between 1875 and 1914, whether portraits, or historical or other dramatic scenes. It has 50 illustrations and six colour plates of his works, and a photograph of his studio.