Background: Hibernomas are soft tissue tumors that form from lingering brown fat cells and tend to form in locations where brown fat is more prevalent in fetuses and babies. They are uncommon, grow slowly, cause no discomfort, and are benign. Because of its rarity, this tumor type is commonly misdiagnosed as liposarcoma or dismissed altogether. Objective: The objective of this case study was to achieve accurate diagnosis for the rare tumor hibernoma in the thigh. Case report: 33-Years-old female not known to have any chronic medical illness, gastric sleeve before 4 years, cholecystectomy 1 year back, and her condition started 5 year back when she noticed left knee lump. Initially she sought medical advice and was told it is lipoma. She was advised for weight loss. No history of trauma or falling. After she lost weight, it become more prominent with knee pain for the last year. Conclusion: As a result of their rarity and underreporting, hibernomas are frequently misinterpreted as either big lipomas or malignant soft tissue tumors, which necessitate the need of histology in achieving an accurate diagnosis and anticipating intraoperative outcomes. Tumors can only be removed safely through meticulous dissection and ligation of the vasculature, which requires knowledge of the surrounding anatomy.