Objective: To determine association of TPH2 (rs7305115) gene polymorphism with age of MDD cases and controls in Pakistani population. Study Design: Case-control study. Setting: Multidisciplinary Lab in Islamic International Medical College Trust in Collaboration with Psychiatry Department, Railway General Hospital, and Rawalpindi. Period: September 2019 to September 2020. Material & Methods: After taking written informed consent blood samples were drawn from all the participants followed by extraction of DNA using ChelexTM method. Allelic frequencies of TPH2 (rs7305115) gene polymorphism in both cases and controls were determined using Multiplex PCR. Results: Number of participants included in the study were 240, out of which 120 were diagnosed cases of MDD whereas 120 were age and gender matched controls. Both the cases and controls were divided in to three groups on the basis of their ages. In group 1 both subjects aged 15 to 35 years were included and a total of 128 subjects fall under this age group out of which 64 (53.33%) were cases and 64 (53.33%) were controls. In group 2 subjects aged 36 to 55 years were included and a total of 86 individuals were found to be present in this age group out of which 45 (37.5%) were cases and 41(34.1%) were controls and in group 3 subjects aged 56 to 75 years were included and a total of 26 individuals were present in this group out of which 11(9.16%) were cases and 15(12.5%) were controls. Significant association was found between age group 1(15-35 years) and GG genotype with risk of development of MDD (OR: 0.3778, 95% CI: 0.1512-0.9349, P= 0.0338). Conclusion: We have found in the present study that age group 1(15-35 years) with GG genotype of TPH2 gene polymorphism have a significantly increased risk of developing MDD as compared to other age groups in our study.