IL-12 plays a very important role in the development and progress of cancer. IL-12B rs3212227 polymorphism has been reported and many studies have focused on the role of this polymorphism in various cancers. However, the association between IL-12B rs3212227 polymorphism and cancer risk remains controversial. Therefore, we performed a systematic meta-analysis to estimate the overall cancer risk associated with this gene polymorphism and to quantify any potential between-study heterogeneity. PubMed and Embase databases were searched for case-control studies published up to April 1, 2012 that investigated IL-12B rs3212227 polymorphism and cancer risk. Odds ratios (OR) with 95 % confidence intervals (95 % CI) were used to access the strength of this association. Heterogeneity among articles and publication bias were also verified. Ten studies with 2,954 cancer patients and 3,276 healthy controls were included. This meta-analysis showed that there was a significant association between IL-12B rs3212227 polymorphism and overall cancer risk (CC/AC vs AA: OR = 1.32, 95 % CI = 1.06-1.63). When stratified by cancer type, we found a significant increased risk in cervical and nasopharyngeal cancer (OR = 1.34, 95 % CI = 1.04-1.73; OR = 2.03, 95 % CI = 1.57-2.63, respectively). In the stratified analysis, we also observed a similar association in population-based studies (OR = 1.34, 95 % CI = 1.00-1.80), Asian populations (OR = 1.33, 95 % CI = 1.06-1.67) and European populations (OR = 1.54, 95 % CI = 1.04-2.28). According to the results of our meta-analysis, IL-12B rs3212227 polymorphism probably is associated with a high risk of cancer.