Polymeric porous microspheres can be used as functional vehicles in drug delivery and cell culture. However, the conventional porous microspheres are somewhat complicated with respect to preparation, and limited in composition and controllability. Here we report the preparation of poly(lactic-co-glycolic acid)/calcium carbonate (PLGA/CC) composite microspheres with uniform superficial macropores through a facile single-step method, where CC acts simultaneously as in situ pore-forming agent and reinforcing phase. The SEM images and quantified results from mercury intrusion porosimetry indicated that the size and density of the superficial macropores were highly controllable via changing the starting parameters such as size and content of CC particles and concentration of PLGA. Mouse bone mesenchymal stem cells were cultured on microspheres of different topographies to investigate the cell–substrate interaction. The results showed that cells adhered and grew well on all microspheres, while the topography with smaller and more discrete macropores exhibited the highest proliferation, indicating that cells responded to the topography of the microsphere. This work provides a novel approach to obtain diverse porous composite microspheres designed for tissue repair and study of cell–substrate interaction.