With the aim to improve the compatibility of polycarbonate (PC)/polypropylene (PP) blends, a novel aromatic polycarbonate diol (PCDL) was synthesized by the transesterification reaction, then a series of polycarbonate‐based thermoplastic polyurethane elastomers compatibilizers (TPU‐Gx) with octadecyl side chains were successfully prepared by introducing different content of PCDL and glyceryl monostearate (2,3‐Dihydroxypropyl octadecenoate; GMS). The structures of synthesized products were confirmed by Fourier transform infrared spectroscopy and Nuclear magnetic resonance hydrogen spectroscopy. Thermogravimetry results showed that all TPU‐Gx had good thermal stability. The effects of TPU‐Gx on the compatibilization of PC/PP blends were investigated in the aspect of morphology, mechanical, thermal, and rheological properties. The results showed that all TPU‐Gx could enhance the interfacial adhesion between PC/PP and improve the mechanical properties of PC/PP blends. Among them, the addition of TPU‐G1.5 containing 6.0 wt% PCDL and 1.5 wt% GMS made PC/PP/TPU‐G1.5 blends show the highest impact strength, which increased by 54.1% when compared with that of pure PC/PP blends.