His work in the theatre includes seasons with the Prospect Theatre Company (Richard II and Edward II, 1969-70, Circle of Glory, 1975), the Citizens' Theatre, Glasgow (1970-72), seven national tours and an Olivier Award nomination for his solo performance of Three Men in a Boat (adapted by Nicholas) at the May Fair Theatre (1982), subsequently filmed for Channel 4, recorded by Argo and broadcast on BBC Radio 4. He appears regularly at festivals in his one man shows Funny You Should Sing That and An Evening with Jeremy Nicholas. At the English Music Festival in May 2008 he was the narrator for Practical Cats (Rawsthorne) with the BBC Concert Orchestra under Barry Wordsworth, the first live performance of the work for 54 years.

His leading roles on television have been in The Pickwick Papers, Outside Edge, Wish Me Luck, The Good Companions, six months in Crossroads (its demise in 1987 was announced within four days of him joining the cast), as well as featuring in popular series such as Birds of a Feather, The Upper Hand, Heartbeat, London's Burning and Murder in Mind. He has also appeared (‘mercifully briefly - they are two of the worst films in the history of cinema’) in Turtle Diary and Ishtar. Nicholas was the voice of Lionel in all 39 episodes of Budgie the Little Helicopter. He will also provide the role of Charlie in the UK version of Thomas and Friends from the thirteenth season onwards.

He has written and presented over sixty radio features for BBC Radio 2, 3 and 4 on a variety of subjects on subjects ranging from Latin, comic songs, and the Shipping Forecast to Korngold, Cziffra, Ronald Frankau and Harry Graham. In 1996 he won the Sony Radio Gold Award for Best Arts Programme. His own radio series have included The Shellac Show (BBC Radio 3), The Jeremy Nicholas Anthology (BBC Radio 2) and The Tingle Factor and Personal Records (BBC Radio 4). He has adapted and/or read more than twenty books for radio and spoken word recordings. His dramatisation of Keble Howard's comic masterpiece The Fast Gentleman was broadcast on BBC Radio 4 in 2000. He was responsible for the concept and compilation of all eight of EMI’s best-selling CDs Hello ChildrenEverywhere based on his series for BBC Radio 4.

Nicholas has composed the music for numerous stage plays (among them the world premiere and West End productions of Tennessee Williams’s Vieux Carré) and four major television plays. His songs and instrumental music have been recorded by Sarah Walker & Roger Vignoles, Marc-André Hamelin, duo-pianists Nettle & Markham, the Grimethorpe Colliery Band and organist Kevin Bowyer.

He is Director of Music for the Deanery Church of St. Mary, Bocking (Essex) and President of the Jerome K. Jerome Society.

He is the author of three reference books on classical music, biographies of Chopin and Leopold Godowsky, a collection of light verse (Raspberries and Other Trifles) and an album of comic songs (Funny You Should Sing That) culled from the more than 150 he wrote for such programmes as Radio 4’s Stop the Week (1978-91). His latest book, The Great Composers, was published in October 2007. Nicholas has written the booklets for over 80 classical CDs, including the recording of his verses for Carnival of the Animals released last year. He is a regular contributor to Gramophone, International Piano and Classic FM magazines as writer and critic.