Inherited variance in the IL-12B gene is associated with susceptibility to Chlamydia trachomatis-induced tubal factor infertility and disease severity. In this study, our aim was to discover how polymorphisms in IL-12-coding genes influence C. trachomatis-induced immune responses and IL-12 production. The study population consisted of 240 women. IL-12A and IL-12B single nucleotide polymorphisms (SNPs) were determined from isolated DNA using the Sequenom system with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. We studied lymphocyte proliferative (LP) responses to C. trachomatis strains E and F elementary bodies (EBs) and recombinant chlamydial heat-shock protein 60 (CHSP60) antigen. IL-12p40 and IL-12p70 levels were measured using the BD Flex Set method. We found a statistically significant association between the C. trachomatis EB antigen-specific LP response and the rs2853694 SNP (P = 0.02). Our study demonstrates that the IL-12 cytokine family is involved in C. trachomatis-specific immune responses. Moreover, C. trachomatis-induced IL-12 production and the IL-12B rs2853694 SNP partially explain individual variation in the C. trachomatis LP response.