Background: Obesity rates are disproportionately high among Latinas living in the United States. Few community-based weight management studies have focused on Latina immigrants living in emerging Latino communities. The purpose of this study was to develop and pilot test a theory-based, promotora-delivered, peer support weight loss intervention for Latina immigrants to be administered in a community setting. We employed participatory methods to develop an 8-week program grounded in self-determination theory. Overweight Latina immigrants were recruited to participate in a quasi-experimental pilot study. Data collected pre and post-intervention included height, weight, fasting lipids, glucose, dietary practices, physical activity and depressive symptoms. Results: Twenty-two women completed the intervention. Mean age was 36, mean time in the U.S. was 12 years; the majority was from Mexico. Mean BMI was 33; 68% had a family history of diabetes. The intervention resulted in statistically significant weight loss (mean 2.1 kg, SD 2.6, p < 0.001); mean change in weight remained significant when compared with that of a historical control group (-2.1 kg vs 1.10 kg, p < 0.01) but was attenuated at 6 months. Levels of moderate physical activity increased significantly (p < 0.05) and dietary practices improved (p < 0.01) and remained significant at 6 months. Notably, depressive symptoms also improved (p = <0.001). Conclusions: This theory-based, promotora-delivered intervention resulted in significant weight loss among a sample of Latina immigrants at 8 weeks. Future studies are needed to test the impact of an extended peer support intervention on long-term weight management.