Schizophrenia is a complex genetic disorder to which genetic variation in the glutamatergic signaling pathways is believed to play a substantial role in the etiology of the disease. Association studies have implicated the N-methyl-D-aspartate receptor subunit gene, GRIN1, as a candidate gene for schizophrenia. In this report, we used a case control study to establish the possible association between the G1001C polymorphism in the GRIN1 gene promoter region and schizophrenia in an Iranian cohort of 200 unrelated patients and 200 controls. The allelic and genotypic frequencies of the polymorphism were determined using polymerase chain reaction restriction fragment length polymorphism. Data analysis using logistic regression and the Mantel–Haenszel chi-square test revealed a strong association between the G1001C polymorphism and schizophrenia (CG genotype: odds ratio (OR)′=′2.12, 95% confidence interval (CI) 1.34–3.48, P′=′0.001 and CC genotype: OR′=′29.10, 95% CI 3.40–565.78, P′<′0.001). Furthermore, the C allele is significantly associated with an increasing risk of schizophrenia.