[1] The family moved repeatedly, first to Alsace, and then to Smila, 200 km from Kyiv, while Loeffler was still a small child, next to Debrecen, in Hungary, where his father Karl taught at the Royal Academy of Agriculture.

He was a friend of Eugène Ysaÿe, Dennis Miller Bunker, and John Singer Sargent (who painted his portrait), also of Gabriel Fauré and Ferruccio Busoni (both of whom dedicated works to him), and later of George Gershwin.

A man of wide culture and refined taste, he developed an idiom deeply influenced by contemporary French and Russian music, in the traditions of César Franck, Ernest Chausson and Claude Debussy, and also by Symbolist and "decadent" literature.

Loeffler often cultivated unusual combinations of instruments, and was one of the earliest modern enthusiasts for the viola d'amore, which he discovered in 1894 and wrote parts for in several scores as well as arranging much music for it.

His notable students include Arthur Hartmann, Kay Swift, Samuel Gardner and Francis Judd Cooke, who studied with him for two years in Medfield, Massachusetts.

His best-known works include the symphonic poems La Mort de Tintagiles (after Maeterlinck), La Bonne Chanson (after Verlaine), A Pagan Poem (after Virgil), and Memories of My Childhood (Life in a Russian Village), as well as the song-cycle Five Irish Fantasies (to words by W. B. Yeats and Heffernan), and the chamber works Music for Four Stringed Instruments and Two Rhapsodies for oboe, viola and piano.