Investigating seasonal variation in health and mortality helps understand disease dynamics and environmental health exposures. Using four available rounds of India's Demographic and Health Surveys (DHS), this paper examines seasonality in infant mortality in India. I use information on the birth month-year, survival status within the first year of life, and age (in months) at death (if the infant died) of more than 330,000 children born between 1989 and 2014 to estimate period mortality rates between ages 0 and 1 for each calendar month. Relative to the spring months, infant mortality is higher in the summer, monsoon, and winter months. If the mortality conditions in the spring months were prevalent throughout the year, would have been less by 10.8 deaths per 1,000 infant alive per year in early 1990s and 4.1 deaths per 1,000 per year in the mid-2010s. Seasonal variation in infant mortality is higher among children born in less wealthy households, among children of less educated mothers, in rural areas, and in poorer regions. Although seasonality in infant mortality has attenuated over-time, seasonal variation in the early-childhood disease environment remains a concern, particularly in rural areas. These results highlight the multiple environmental health threats that infants in India face, and the limited period within a year when these threats are less salient.