ZnO hollow microspheres with a diameter of approximately 1.4 μm were successfully synthesized by a facile one-step chemical precipitation method using trisodium citrate dihydrate as a morphology control agent. The ZnO hollow microspheres consisted of nanoplates and had good dispersibility. Control experiments revealed that trisodium citrate dihydrate played an important role in regulating the morphologies of ZnO products. The morphology of the ZnO product evolved from nanowires to hollow microspheres with the addition of trisodium citrate dihydrate. The sensor response of ZnO hollow microspheres toward 100 ppm n-butanol reached 86.6 at the optimum operating temperature of 340 °C, which was approximately three times higher than that of ZnO nanowires. In addition, the ZnO hollow microspheres also displayed good selectivity and long-term work stability toward n-butanol. The excellent gas sensing performance of ZnO hollow microspheres may be ascribed to the unique hollow sphere structure with high exposed polar crystal surface.