Acute exertional compartment syndrome (AECS) is increasingly recognised as an emergency presentation requiring urgent surgical intervention. This can theoretically affect any myofascial compartment, but is rare around the shoulder, with very limited literature relating to AECS of the supraspinatus muscle. It is vital for the treating medical team to have an index of suspicion for this condition in patients presenting with acute severe shoulder pain secondary to exertion, and act promptly to assess and investigate. Clinical assessment can be combined with important adjunctive investigations including magnetic resonance imaging and compartment pressure measurement, and if the diagnosis is confirmed or strongly suspected, emergency fasciotomy should be performed. We present a case of a patient with AECS of the supraspinatus, treated with emergency fasciotomy, who made a good long-term recovery.