Burn trauma results in prolonged hypermetabolism and skeletal muscle wasting. How hypermetabolism contributes to muscle wasting in burn patients remains unknown. We hypothesized that oxidative stress, cytosolic protein degradation, and mitochondrial stress as a result of hypermetabolism contributes to muscle cachexia post-burn. Patients (n=14) with burns covering >30% of their total body surface area (TBSA) were studied. Controls (n=13) were young healthy adults. We found that burn patients were profoundly hypermetabolic at both the skeletal muscle and systemic levels, indicating increased oxygen consumption by mitochondria. In skeletal muscle of burn patients, concurrent activation of mTORC1 signaling and elevation in the fractional synthetic rate (FSR) paralleled increased levels of proteasomes and elevated fractional breakdown rate (FBR). Burn patients had greater levels of oxidative stress markers, as well as higher expression of mtUPR-related genes and proteins, suggesting that burns increased mitochondrial stress and protein damage. Indeed, upregulation of cyto-protective genes suggest hypermetabolism-induced oxidative stress post-burn. In parallel to mtUPR activation post burns, mitochondrial specific proteases (LONP1 and CLPP), and mitochondrial translocases (TIM23, TIM 17B, and TOM40) were upregulated, suggesting increased mitochondrial protein degradation and transport of pre-protein, respectively. Our data demonstrate that proteolysis occurs in both the cytosolic and mitochondrial compartments of skeletal muscle in severely burned patients. Increased mitochondrial protein turnover may be associated with increased protein damage due to hypermetabolism-induced oxidative stress and activation of mtUPR. Our results suggest a novel role for the mitochondria in burn-induced cachexia.