The creep behavior of two PM superalloys, U720Li and RR1000, each alloyed with trace amount of Sc, was systematically investigated. Findings reveal that RR1000 alloy with 0.064 wt.% Sc (R-0.064) demonstrates superior creep resistance compared to U720Li alloy with 0.043 wt.% Sc (U-0.043), at 650 °C and 1000 MPa, and the primary creep mechanisms in both alloys are identified as dislocation shearing and precipitate bypassing. When tested at 700 °C and 700 MPa, the U-0.043 alloy predominantly exhibits micro-twinning and dislocation bypassing, while the R-0.064 alloy engages in extended stacking fault shearing of γ′ precipitate, dislocation bypassing and climb. At 750 °C and 460 MPa, dislocation bypassing and climb emerge as the main creep mechanisms for both alloys.