Ludwigia octovalvis (Jacq.) P.H. Raven is widely used in traditional medicine for different illnesses, including diabetes and hypertension. However, its impact on lipotoxicity and metabolic syndrome in vivo has not been addressed. Therefore, the aim of this study was to evaluate the effects of this plant on the metabolic syndrome parameters in a C57BL6J mouse hypercaloric diet model. L. octovalvis hydroalcoholic extract and its ethyl acetate fraction (25 mg/kg/day) were used for sub-chronic assessment (10 weeks). Additionally, four subfractions (25 mg/kg) were evaluated in the postprandial triglyceridemia test in healthy C57BL6J mice. The hydroalcoholic extract and ethyl acetate fraction significantly decreased body weight gain (−6.9 g and −1.5 g), fasting glycemia (−46.1 and −31.2 mg/dL), systolic (−26.0 and −22.5 mmHg) and diastolic (−8.1 and 16.2 mmHg) blood pressure, free fatty acid concentration (−13.8 and −8.0 μg/mL) and insulin-resistance (measured by TyG index, −0.207 and −0.18), compared to the negative control. A postprandial triglyceridemia test showed that the effects in the sub-chronic model are due, at least in part, to improvement in this parameter. L. octovalvis treatments, particularly the hydroalcoholic extract, improve MS alterations and decrease free fatty acid concentration. These effects are possibly due to high contents of corilagin and ellagic acid.