Insufficient mitochondrial quantity in brown adipose tissue (BAT) causes defective thermogenesis and positive energy balance, which is coupled with the development of obesity. Whether disturbance of mitochondrial quality affects BAT function remains unknown. Here, we describe that the brown adipocyte-specific Leucine-rich PPR motif-containing protein knockout mice (LrpprcBKO) exhibited mitochondrial electron transport chain (ETC) proteome imbalance and a complete loss of the -adrenergic-stimulated thermogenesis at room temperature (RT), due to specific reduction of mtDNA-encoded genes. However, the LrpprcBKO mice were lean at normal chow and were protected against high-fat-diet-induced metabolic abnormalities, such as obesity, insulin resistance, adipose inflammation, hepatic steatosis, and hypertriglyceridemia. The beige adipocytes in inguinal white adipose tissue were expanded in LrpprcBKO mice at RT, but not at thermoneutrality. However, BAT thermogenic defects and metabolic benefits were present in LrpprcBKO mice regardless of ambient temperatures. Collectively, our results reveal that a thermogenesis-incapable BAT with mitochondrial ETC proteome imbalance can improve systemic metabolism, suggesting BAT’s contributions to thermoregulation and systemic metabolism can be uncoupled.