Acute compartment syndrome is one of the few true orthopaedic emergencies. Timely management is essential to prevent permanent sequelae. This video describes a patient with acute compartment syndrome of the arm and demonstrates the surgical technique for arm fasciotomy via a lateral approach. The patient is a 45-year-old man who presented 2 days after a crush injury to his right arm. Physical examination findings are consistent with acute compartment syndrome of the arm, and fasciotomy is indicated. Given the substantial anteromedial arm blistering present, a lateral approach was selected for arm fasciotomy. The video highlights the surgical technique for arm fasciotomy via a lateral approach. Diagnostic criteria for acute compartment syndrome and indications for fasciotomy are presented, and the published outcomes of fasciotomy are discussed. Compartment syndrome of the arm is rarely reported. Timely fasciotomy is essential to preserve function of the extremity. Orthopaedic surgeons must be familiar with the technique for arm fasciotomy and understand the importance of immediate intervention for patients in whom acute compartment syndrome is suspected.