In 2023, Coolmore Stud expanded the owner partnership of the horse to include Derrick Smith, Michael Tabor, Westerburg and Rocket Ship Racing.
[2] Sierra Leone made his debut on November 4 in a maiden special weight event over 1 mile at Aqueduct Racetrack.
Sierra Leone poked his head in front of leader Dornoch with a furlong to run but the latter fought back and won by a nose in a time of 1:50.30 over a muddy, sealed track.
[7] On February 17, 2024, Sierra Leone began his three-year-old campaign in the Grade II Risen Star Stakes at Fair Grounds Race Course in New Orleans.
Starting as the 2/1 favorite, he was unhurried early on and uncorked a winning rally in the stretch, prevailing by a half-length in the 1+1⁄8-mile event.
He rallied from ninth to overhaul Just a Touch late in the stretch to win by 1+1⁄2 lengths with his Remsen rival Dornoch finishing fourth.
[10] Returning to Saratoga Race Course on July 27 for the Grade 2 Jim Dandy Stakes, Sierra Leone trailed in last place early, then made a significant move around the final turn.
[12] On November 2, 2024, Sierra Leone won the Breeders' Cup Classic, defeating two-year-old champion Fierceness by 1 ½ lengths.
After starting near the back of the field, he took advantage of a fast early pace and unleashed a late kick to prevail in a final time of 2:00.78.