Purpose: Describe the demographic, injury-related, treatment-related, and outcome-related characteristics of patients who undergo fasciotomies for acute upper arm compartment syndrome (ACS). Methods: From January 1, 2006, to June 30, 2015, 438 patients with a diagnosis code of upper extremity (including hand, forearm, arm, and shoulder) compartment syndrome at two tertiary care centers were identified. Of those patients, 423 were excluded for a diagnosis other than upper arm ACS or incomplete documentation. A final cohort of 15 adult patients with acute upper arm compartment syndrome treated with fasciotomy was included. The electronic medical record for patient-related variables, lab data, mechanism of injury, presence of additional injuries, and treatment-related variables were reviewed. Results: The mean age of our cohort was 52 years, and 73% were male. The most common mechanisms of injury were blunt trauma (20%), vascular injury (20%), oncologic resection (13%), and infection related to intravenous drug use (13%). Humerus fractures and biceps tendon ruptures were associated with 13 and 27% of the cases, respectively. More than two-thirds of the patients had elevated international normalized ratios (INR). While 27% of cases underwent fasciotomy within 6 h after injury, seven patients (47%) underwent fasciotomy more than 24 h after injury. Six patients had no major deficits, while 7 patients had long-term deficits. Conclusion: Upper arm ACS is a potentially devastating condition that can be seen after blunt trauma, vascular injury, oncologic resection, and intravenous drug use. Clinicians should have high suspicion in cases of elevated INR and biceps tendon rupture.