As a freshman at Oregon State in 2016, Larnach played in 28 games, hitting .157/.271/.176 with three runs batted in (RBI) over 51 at bats.[3] As a sophomore in 2017, he played in 60 games and hit .303/.421/.429 with three home runs and 48 RBI in 198 at bats.[4] After the 2016 and 2017 seasons, he played collegiate summer baseball with the Falmouth Commodores of the Cape Cod Baseball League, where he was named a league all-star in 2016.[5][6]
In 2018, as a junior, Larnach was named to the Pac-12 All-Conference Team.[7] During Game 2 of the 2018 College World Series against the Arkansas Razorbacks, with Arkansas and OSU tied 3-3 in the top of the ninth inning, Larnach hit a two out, two-run home run to give the Beavers a 5-3 lead.[8] Oregon State went on to win the game and the 2018 College World Series.[9] He was named to the All-Tournament Team.[10] Larnach finished his junior season with a .348 batting average, 19 home runs, and 77 RBIs.[11]
On May 7, 2021, Larnach was selected to the 40-man roster and promoted to the major leagues for the first time.[21] Larnach made his MLB debut the next day as the starting left fielder against the Detroit Tigers.[22] The Twins optioned Larnach to the Triple-A St. Paul Saints on August 16.[23] He finished his rookie campaign appearing in 79 games and hitting .223/.322/.350 with 7 home runs and 28 RBI.
In 2022, Larnach played in 51 games for Minnesota, hitting .231/.306/.406 with 5 home runs and 18 RBI. On June 28, 2022, Larnach underwent bilateral surgical repair on a core muscle strain he had suffered days earlier. Initially expected to sideline him six weeks, the procedure ended Larnach’s season.[24] In 2023, he played in 58 games for Minnesota, batting .213/.311/.415 with career–highs in home runs (8) and RBI (40).[25]
Larnach was optioned to Triple–A St. Paul to begin the 2024 season.[26]
^"Larnach discusses family roots". MiLB.com. August 13, 2019. Archived from the original on August 13, 2019. Retrieved August 13, 2019. My uncle Brian played football for three different NFL teams. He played for the Green Bay Packers, the Atlanta Falcons and the Chicago Bears. He won a championship with [the Bears].