Sydney Keir started her formal training in Toronto, Ontario at Canada's National Ballet School and Karpov Ballet Academy. She later relocated to New York, where she attended the Ailey Fordham BFA Program, a joint program between Fordham University and the Ailey School, where she completed a double major in Dance and Communications/Media Studies. She has performed with the Alvin Ailey American Dance Theater, Canadian Opera Company, Hit & Run Dance Productions, National Ballet of Canada, Dusk Dances, Nathaniel Hunt Dance Project, Boston Dance Theater, Cadence Contemporary Ballet, Karpov Ballet, Ballet Jorgen, and Buglisi Dance Theatre. Sydney has performed alongside The Alvin Ailey American Dance Theatre in their 2017 City Center Season and 2018 Lincoln Center Season. Sydney was also an original cast member of the international touring show Isadora produced by Ardani Arts Management that featured Natalia Osipova. In 2019, she made her debut with the Canadian Opera Company in Robert Wilson’s Turandot. She can also be seen dancing on screen in Netflix's Umbrella Academy and Amazon Prime's All or Nothing.