Background: Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a ligand dependent transcription factor involved in various processes, including carcinogenesis. We aimed to investigate any possible association of the PPAR gamma Pro12Ala (rs1801282) polymorphism with risk of developing gastric cancer (GC). Patients and Methods: A hospital based case control study was designed covering 50 patients with GC and 120 healthy controls. The frequencies of PPAR gamma Pro12Ala (rs1801282) were determined using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Results: The Ala12 allele of the PPAR gamma Pro12Ala G gene was associated with a 1.95 fold increased risk of GC development (p: 0.022; 95% CI: 1.58-2.40). Subgroup analyses showed that the same allele was also associated with metastasis (p: 0.000; OR: 4.09; 95% CI: 2.273-7.368) and differentiation (p: 0.004; OR: 1.95; 95% CI: 1.335-2.875) in patients with GC. Conclusion: This study suggests that the PPAR gamma Pro12Ala G (Ala12) allele might be associated with development, differentiation and metastatic process of GC in the Turkish population. Further studies conducted in larger study groups and in different ethnic populations will be needed to clarify the exact role of the PPAR gamma Pro12Ala polymorphism in GC.