Background: Chromodomain helicase DNA-binding protein 5 (CHD5), which belongs to a superfamily of SWI2/SNF2-related ATPases, is a conventional tumor suppressor gene encoding a unique combination of functional domains followed by a helicase domain and a DNA-binding domain. To date, CHD5 protein was detected in brain region and appeared to be enriched in neurons.\n \nMethodology/Principal Findings: We genotyped CHD5 tagging single-nucleotide polymorphism (tSNP) rs1534997 by TaqMan probes in two independent cohorts: the discovery study including 264 cases and 255 controls (North China); and the replicative study including 477 cases and 471 controls (South China). The discovery cohort revealed that genotype AA in cases was less than that from controls (adjusted OR 0.62, 95% CI 0.42-0.91, P = 0.009). This protective quality increased in a dose-dependent manner as genotype AA decreased (Ptrend = 0.004). Corresponding relevance for genotype AA was showed in the replicative and combined cohorts (replicative: adjusted OR 0.58, 95% CI 0.44-0.79, P = 6.328×10-4, Ptrend = 2.053×10-4; Combined: adjusted OR 0.59, 95% CI 0.47-0.76, P = 7.167×10-5, Ptrend = 8.905×10-6). \n\nConclusion: Our study indicated that rs1534997 of CHD5 might protect against the risk of paranoid schizophrenia in a dose-dependent manner.