Anomalous polyimide (PI) nanoparticles with controllable morphology, i.e., porous hollow structures, hollow structures, or bowl-like structures, were fabricated by blending a second polymer with poly(amic acid) (PAA, the precursor of PI) through the reprecipitation method and subsequent imidization. The phase separation between PAA and the porogen induced the formation of various hollow PI nanoparticles. The hollow morphology was mainly affected by the compatibility/interaction between PAA and the porogen. Hollow PI nanoparticles with superficial pores (ca. 30 nm), smooth surface, or holes in their surfaces can be obtained by selecting a suitable porogen, respectively.