Fiona Tonkin was born in Singapore in 1961, but brought up and trained in dance in New Zealand initially by Lorraine Peters. Fiona Tonkin began her career with Southern Ballet in Christchurch before joining Royal New Zealand Ballet in 1979. In 1980 she was invited by Marilyn Jones, then artistic director of the Austalian Ballet, to come to Australia. Tonkin joined the Australian Ballet that year, was promoted to coryphee in 1982, soloist in 1984, senior artist in 1986 and in 1987 reached the rank of principal. With the Australian Ballet she danced leading roles in all the major classical works in the company's repertoire, and received much acclaim in many of the company's one act works. During her career with the Australian Ballet Tonkin guested with the Kirov Ballet (1990) and appeared in Rudolf Nureyev's farewell tour (1991). She also travelled overseas on a study scholarship in 1988 spending time with Stuttgart Ballet being coached by Marcia Haydee and working with Yvette Chauvire in Paris.
Tonkin resigned from the Australian Ballet at the end of 1993 and returned to New Zealand where she completed a Bachelor of Arts at the University of Canterbury. While studying she also taught in both Australia and New Zealand and in 1999 completed an advanced teaching course for professional dancers at the Australian Ballet School. In 2000 Tonkin was appointed rehearsal director of Royal New Zealand Ballet, which was then directed by Mats Skoog. In 2002 she accepted Skoog's invitation to join him in London as assistant artistic director of English National Ballet. Tonkin returned to the Australian Ballet in 2003 as principal coach and ballet mistress.