The microstructure evolution and creep behavior of a novelly designed as-cast Ni3Al-based superalloy with multiphase configuration are investigated by high-temperature annealing treatments. The as-cast microstructure comprises dominant �����+�� dendritic and less (~19.37 vol%) interdendritic �� areas, annealing treatments at 1160���1280 ��C promoted the growth of �������� phase in the �����+�� dendrite, during which the interdendritic �� phase aggregated and coarsened rapidly in width with keeping its relatively constant volume fraction. Meanwhile, the annealing treatments significantly promoted the precipitation of quasi-spherical ��-Cr phase particles within the �� phase. The original as-cast microstructure exhibited inferior creep resistance at 800 ��C/200 MPa with the shortest creep rupture life of 194 h, however, the annealing treatments at 1160���1280 ��C prolonged the creep rupture life to beyond 611 h. Although the steady-state creep rate was gradually reduced with increasing annealing temperatures, the creep ductility was degraded by higher-temperature annealing at 1240 and 1280 ��C compared with original as-cast microstructure. The 1160 ��C annealed microstructure exhibited the longest creep rupture life of 665 h and the maximum creep strain to fracture of 3.21%, while the minimum steady-state creep rate was obtained on account of the largest �������� phase sized 0.91 ��m after annealing at 1280 ��C. Despite its positive role in the castability, thermoplasticity and weldability of the explored multiphase Ni3Al-based superalloy, interdendritic �� phase has negative effects on the creep properties due to its incoherent existence with the dominant �����+�� dendrite.