Epigallocatechin gallate (EGCG) is the predominant bioactive catechin in green tea, and it has been ascribed a range of beneficial health effects. Current increases in obesity and non-alcoholic fatty liver disease (NAFLD) rates represent a persistent and burdensome threat to global public health. While many clinical studies have demonstrated that EGCG is associated with positive effects on various health parameters, including metabolic biomarkers, waist circumference, and body weight when consumed by individuals affected by obesity and NAFLD, there are also some reports suggesting that it may entail some degree of hepatotoxicity. The present review provides a comprehensive summary of the extant clinical findings pertaining to the safety and effectiveness of EGCG in managing obesity and NAFLD, with a particular focus on how treatment duration and dose level affect the bioactivity of this compound.