The Pirates acquired Callihan from the Reds in exchange for Kyle Nicolas on Wednesday.
Callihan made his MLB debut last season with Cincinnati, seeing action across four games. The 25-year-old utilityman recorded a single, an RBI and one strikeout across six plate appearances. Callihan will compete for a depth role in Pittsburgh after he showed impressive bat-to-ball skills at the Triple-A level in 2025, slashing .303/.410/.528 with four home runs, 12 RBI, 19 runs scored, six stolen bases and a 16:29 BB:K across 106 trips to the plate.