Background: Infertility is a important reproductive health issue that affects people worldwide. Despite its psychosocial and public health implications, population-level evidence on primary and secondary infertility remains limited. The purpose of study was to estimate the prevalence and determinants of primary and secondary infertility among married women of reproductive age in India using National Family Health Survey-5 (NFHS-5) data. Methods: A cross-sectional secondary data analysis of NFHS-5 (2019-2021) was conducted among 512,408 currently married women aged 15-49 years. Descriptive analysis was used to estimate prevalence of primary and secondary infertility. Chi-square test and multivariable logistic regression analysis were performed to identify factors associated with infertility. Results: The prevalence of primary infertility was 3.28% (95%CI:3.23-3.33), while secondary infertility was 13.9% (95%CI:13.85-14.05), indicating a higher burden of secondary infertility. Considerable state-wise variation was observed. Higher prevalence of primary infertility was reported in Karnataka, Telangana, Lakshadweep, and Goa, whereas secondary infertility was highest in Mizoram, Meghalaya, and Ladakh. Urban residence, smoking, overweight/obesity, thyroid disorders, and diabetes were significantly associated with both primary and secondary infertility. Delayed age at first marriage was positively associated with primary infertility, whereas increasing age was strongly associated with secondary infertility. Educational attainment and wealth index demonstrated varying associations across infertility types. Conclusion: Infertility affects a considerable proportion of married women in India, with secondary infertility contributing the larger share of the burden. The substantial regional and socio-demographic disparities observed highlight the need to integrate infertility prevention, surveillance, and equitable access to fertility care within reproductive health programs in India.