Objectives In this paper we examine the role of mothers’ nutritional status and socio-biological aspects in determining the birth weight of their most recent child. Methods We used data from the second Indian National Family Health Survey conducted in 1998–1999. Analysis is based on children born within 12 months prior to the survey date (N = 10,042). We used a subjective measure of the size of infant at birth as an indicator for birth weight and employed logistic regression to estimate the effect of BMI and other determinants on birth weight of children in India as a whole and for 17 states separately. Results and Conclusions Results show that mothers’ nutritional status is the most important determinant of newborn children’s birth weight. Safe drinking water, use of antenatal care and iron deficient anaemia were also significant contributors to low birth weight. Mothers’ BMI impact is more pervasive across India than the impact of other factors on birth weight.