The key clock protein Period2 (Per2) has been suggested to play an essential role in regulating endothelial function. It also regulates the expression of plasminogen activator inhibitor-1, but its role in stroke development has not been studied. To explore the possible association between Per2 and ischemic stroke (IS), 479 Chinese IS patients and 306 healthy controls were recruited, and five tag single nucleotide polymorphisms representing the Per2 locus were genotyped using the Sequenom MassARRAY system. A significant difference was observed in the genotypic distribution (p=0.014) and allele frequency (p=0.005) of rs10462023, with carriers of the G allele being more prone to developing IS. After adjusting for possible risk factors including smoking, alcohol use, and history of hypertension and diabetes, a significant association was still apparent. Haplotype analysis also supported the association between Per2 and IS. This study suggests that Per2 variations are associated with IS and may represent genetic risk factors for IS in a Chinese population.