Introduction. A Morel-Lavallée lesion (MLL) is a rare and aesthetically concerning condition caused by a shearing force between subcutaneous fat and underlying fascia. Subsequent seroma formation occurs after the initial trauma of a crush injury, ligamentous sprain, or abdominal liposuction. Misdiagnosed lesions lead to inadequate treatment and are a source of chronic pain. Case Report. The case of a 33-year-old woman who presented with a large, painful subacute MLL of the left thigh after being run over by a truck 3 weeks prior is reported. Physical examination revealed severe hyperesthesia and fluctuance of the left thigh. After confirmation of the fluid collection by X-ray and computed tomography angiogram, the authors performed liposuction of the cavity and seroma wall to evacuate and treat the lesion. Postoperative care consisted of a temporary drain, thigh compression, and oral antibiotics. Immediate reduction in size was appreciated intraoperatively with no reaccumulation of fluid at postoperative visits on week 1 and week 6. The pathology report confirmed seroma etiology, and all cultures of the fluid returned negative. At the end of her postoperative course, the patient reported a reduction in pain and no recurrence of her symptoms. Conclusions. This case of MLL was diagnosed early and successfully treated with liposuction, resulting in an acceptable cosmetic outcome. It is the authors’ hope that this case report will lead to earlier diagnosis and proper treatment of MLLs.