['Estrogen-related receptors (ERRs) are important regulators of energy metabolism. Here we investigated the hypothesis that ERRγ impacts on differentiation and function of brown adipocytes.', 'We characterize the expression of ERRγ in adipose tissues and cell models and investigate the effects of modulating ERRγ activity on UCP1 gene expression and metabolic features of brown and white adipocytes.', 'ERRγ was preferentially expressed in brown compared to white fat depots, and ERRγ was induced during cold-induced browning of subcutaneous white adipose tissue and brown adipogenesis. Overexpression of ERRγ positively regulated uncoupling protein 1 (UCP1) expression levels during brown adipogenesis. This ERRγ-induced augmentation of UCP1 expression was independent of the presence of peroxisome proliferator-activated receptor coactivator-1 (PGC-1α) but was associated with increased rates of fatty acid oxidation in adrenergically stimulated cells. ERRγ did not influence mitochondrial biogenesis, and its reduced expression in white adipocytes could not explain their low expression level of UCP1.'] Does eRRγ enhance UCP1 expression and fatty acid oxidation in brown adipocytes?