Fu brick tea is one of the most famous microbially fermented teas that has received considerable attention owing to its promising anti-obesity capacity; however, the underlying mechanisms of its action remain largely unexplored. Herein, an eight-week oral administration of Fu brick tea aqueous extract (FTE) was observed to dose-dependently reduce body weight and abnormal fat accumulation for inguinal white adipose tissue, stimulate beige-fat development and thermogenesis in the brown adipose tissue of mice fed with a high-fat diet (HFD) (p < 0.05). FTE ameliorated HFD-induced gut dysbacteriosis and improved the microbiome ecology such that it exhibited an increased capacity to reduce the host adiposity, abnormal glycometabolism, and hepatic steatosis. FTE increased the abundance of beneficial bacteria strains, e.g., Lactobacillus, Roseburia, Bifidobacterium, Akkermansia, Parabacteroides, and Prevotella, accompanied with the improved production of short-chain fatty acids (p < 0.05). Moreover, the PICRUSt pathway analysis revealed that FTE upregulated genes enriched in pathways of the carbohydrate metabolism, signaling molecules and immune system. As a rising star of post-fermented teas with the low cost, high accessibility and confirmed health benefits, our findings indicate the beneficial impacts of Fu brick tea on the promotion of adipose browning and thermogenesis in association with gut microbiota reconstructions, paving the way to restrict obesity and its associated metabolic diseases.