The objectives of this study were to describe gestational weight gain (GWG) trends and identify predictors of GWG among WIC participants in Southern California, 84 % of whom are Hispanic. Using descriptive statistics and multiple logistic regression, we examined WIC data on 23,840 Hispanic women with full term pregnancies who enrolled in WIC at first trimester and had their last prenatal WIC visit within 1 month or less of their delivery date. Overall, 23.9 % of women exceeded IOM recommendations. Among Hispanic English speakers (HES), 30 % exceeded IOM recommendations compared to 18.7 % of Hispanic Spanish speakers (HSS). Among Hispanic mothers who are less than 20 years of age, 28.9 % exceeded IOM guidelines compared to 19.8 % of Hispanic mothers 35 or older. Among those who started pregnancy overweight or obese, 30.5 % exceeded IOM recommendations versus 12.1 % of those with normal BMI. Multiple logistic regression showed that the odds of exceeding the IOM recommendations were 42 % lower for HSS versus HES, decreased by 2 % for every 1 year increase in age, and increased by 5 % for every one unit increase in BMI at first trimester. Poverty level and health care coverage were also significant predictors of GWG. Given the wide reach and high quality of height/weight measurements taken by the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) Program, WIC administrative data have significant potential to help fill the existing gaps in GWG surveillance, a much needed step for forming policy and designing effective interventions.