The daughter of a teacher and a farmer (Eimir and Charles), Blackmore grew up on a dairy farm in Killenaule, County Tipperary, Ireland, and first started riding ponies at just two years of age.
[4] Blackmore rode her first winner as an amateur jockey on 10 February 2011, when Stowaway Pearl, trained by John Joseph "Shark" Hanlon, won the Tipperary Ladies’ Handicap Hurdle at Thurles.
[7] Blackmore's first Grade 1 race victory in Ireland came in April 2019 when Honeysuckle won the Mares' Novice Hurdle Championship Final at Fairyhouse.
Blackmore finished the season with 90 winners and took the runner-up spot in the Irish jump racing Champion Jockey competition behind Paul Townend.
[8][9] On 10 April of the same year, Blackmore rode Minella Times to victory in the 2021 Grand National, becoming the first female jockey to win the race.
The gelding, trained by de Bromhead, went off as fourth favourite at 11/1 and, having given Blackmore a "sensational spin", passed the post 6½ lengths in front of stablemate and runner-up Balko Des Flos.
[19] Blackmore was appointed an Honorary Member of the Order of the British Empire (MBE) in the 2023 Special Honours for services to sport.