The proportion of women entering pregnancy overweight or obese has been rising and, in turn, is associated with adverse maternal and fetal outcomes. Gestational weight gain (GWG) exceeding Institute of Medicine (IOM) guidelines further increases health risks and has been independently associated with postpartum weight retention. Hispanic women are disproportionately affected by overweight and obesity, but have had limited access to interventions that promote healthy lifestyles due to cultural, socioeconomic, and language barriers. Therefore, the overall goal of this randomized controlled trial is to test the efficacy of a culturally and linguistically modified, individually-tailored lifestyle intervention to reduce excess GWG, increase postpartum weight loss, and improve maternal metabolic status among overweight/obese Hispanic women.Overweight/obese Hispanic women are recruited in early pregnancy and randomly assigned to a Lifestyle Intervention (n = 150) or a Comparison Health and Wellness (control) intervention (n = 150). Multimodal contacts (i.e., in-person, telephone counseling, and mailed print-based materials) are used to deliver the intervention from early pregnancy (12 weeks gestation) to 6 months postpartum, with follow-up to 1 year postpartum. Targets of the intervention are to achieve IOM Guidelines for GWG and postpartum weight loss; American Congress of Obstetrician and Gynecologist guidelines for physical activity; and American Diabetes Association guidelines for diet. The intervention draws from Social Cognitive Theory and the Transtheoretical Model and includes strategies to address the specific social, cultural, and economic challenges faced by low-income Hispanic women. Assessments are conducted at baseline (~10 weeks gestation), mid pregnancy (24-28 weeks gestation), late pregnancy (32-34 weeks gestation) and postpartum at 6-weeks, 6-months, and 12-months by bicultural and bilingual personnel blinded to the intervention arm. Efficacy is assessed via GWG, postpartum weight loss, and biomarkers of glycemic control, insulin resistance, and cardiovascular disease risk factors. Changes in physical activity and diet are measured via 7-day accelerometer data and 24-h dietary recalls at each assessment time period.Hispanic women are the fastest growing minority group in the U.S. and are disproportionately affected by overweight and obesity. This randomised trial uses a high-reach, low-cost strategy that can readily be translated into clinical practice in underserved and minority populations.NCT01868230 May 29, 2013.