Early in her career she became known for her performance in plays by J. M. Barrie, and is probably best remembered for creating the role of Wendy in Peter Pan.
Another early success was as Oliver Twist in a dramatisation of Charles Dickens's novel staged by Herbert Beerbohm Tree.
Her first important London engagement was at the Court Theatre in 1898, understudying Pattie Browne in the role of Avonia Bunn in Trelawny of the 'Wells', a part that she later played many times in her own right.
[3] She followed this comic role with "an exquisite performance as the hapless, terror-stricken orphan" in Herbert Beerbohm Tree's production of Oliver Twist.
The Observer's critic wrote, "When I say that Miss Hilda Trevelyan's Janet Cannot seemed to me quite perfect there will doubtless be people to tell me that the part has been done better.
[3] One of the most notable of Trevelyan's performances in the 1930s was with Nina Boucicault in a BBC radio broadcast called There's More Magic in the Air, in which they played their original roles of nearly thirty years earlier, in a "composite fantasy" in which Peter Pan and Wendy mingled with Prospero and Ariel.
[9] One of the great successes of the last years of Trevelyan's career was Ian Hay's Housemaster, in which she played Barbara Fane.