Fat embolism syndrome (FES) occurs classically characterized by the combination of acute respiratory failure, neurologic abnormalities, and a petechial rash. Forty-six-year-old female presented to our emergency department with agitation, altered mental status, and drowsiness. We learned that the patient had received a hyaluronic acid (HA) injection into her buttocks at a beauty center a few hours before her admission. She had no skin findings, but she was hypoxemic. She had lung computed tomography (CT) findings bilateral ground-glass opacities and pleural effusion and had multiple cerebral white lesion on brain magnetic resonance images (MRI). Patients presenting to the emergency department with sudden alteration in mental status should be questioned for recent surgical or invasive aesthetic procedures. Fat embolism syndrome should be considered even if the patient has no petechial rash. Brain MRI and lung CT should be the imaging modality of choice in these patients.