Dietary weight loss supplements include a wide range of ingredients. Many ingredients are derived from natural food sources such as green tea. This article presents the composition, mechanisms of action, efficacy, and safety of green tea as a dietary aid to weight loss in overweight and obese adults. While green tea appears to promote energy expenditure and fat oxidation, safety concerns exist when it is consumed as a dietary supplement. Until more evidence-based research is conducted to determine which formulations and dosages are the safest and most effective, green tea should be used with caution as an aid for weight loss.