Apart from theatre, Tom Cullivan has composed in almost all genres except Opera. His catalogue includes a symphony, two piano concertos (the first of which premiered in the National Concert Hall Dublin to an enthusiastic reception in February1982), an extended set of variations for piano and orchestra (which he himself premiered with the Galway Concert Orchestra in 1999) and a number of shorter works for orchestra, notably a "Meditation for Bassoon and Orchestra" and "The March of The Pikemen" premiered by the Cork Symphony Orchestra, conducted by Helen Sheehan in April 2002 and March 2003 respectively. The soloist in the "Meditation" was the Galway bassoonist and conductor, Michael Dooley to whom the composer's sonata for bassoon and piano is dedicated and who gave the work its world premiere in Ludlow in July 2003 accompanied by the Spanish pianist Claudia Vilias.

In addition to the bassoon sonata, Cullivan's chamber work includes five piano sonatas, two sonatas for violin and piano, a sonata each for viola and piano, and cello and piano, two string quartets and two piano quintets. He has also written a variety of choral works, shorter pieces and songs. His "Breffny Ballet" based on the story "Nalla's Child" from Hunt's "Folk Tales of Breffny" and incorporating the traditional mummers play, was premiered by the Sylvia Behan Company at the Players Wills Theatre, Dublin, in 1987.