Infant’s birth weight, especially low birth weight (LBW), are intergenerational issues that will affect the cycle of life. Vegetarian diets are at risk because limited food consumption could cause nutrient deficiencies. This retrospective study aims to determine the relationship between maternal nutritional status (pre-pregnancy body mass index (BMI) and weight gain during pregnancy) and infant’s birth weight among vegetarians in Jakarta. The total sample of 85 children aged 1 month to 5 years was selected purposively. Results showed that the mean of pre-pregnancy BMI of vegetarian mothers is 20.2 kg/m2 (±2.2 kg/m2), pregnancy weight gain is 15.5 kg (±6.4 kg) and infant’s birth weight is 3212 gs (±417.7 gs). Pre-pregnancy BMI and pregnancy weight gain were significantly associated with infant’s birth weight of vegetarians. There is no relationship between pre-pregnancy BMI and pregnancy weight gain. Multivariate analysis found that pre-pregnancy BMI, protein, vitamin B12, iron, and Zn intakes and sex has relationship with infant’s birth weight. It is recommended that vegetarian mothers should get information about the importance of pre-pregnancy nutrition, optimal pregnancy weight gain, and maintaining adequate intake of protein, vitamin B12, iron, and Zn during pregnancy.