Children suffering supracondylar fractures of the humerus are at risk of vascular compromise, which is currently assessed clinically, although other modalities such as angiography, pulse oximetry, Doppler ultrasound and magnetic resonance angiography have been used. We sought to ascertain whether tissue haemoglobin oxygenation (StO2) measurement could distinguish between patients with and without clinical vascular compromise following supracondylar fractures of the humerus. We prospectively observed StO2 using near-infrared spectroscopy in 29 paediatric patients with supracondylar fractures requiring operative manipulation. The injured and uninjured volar forearm compartments were monitored immediately before and after fracture reduction. The relationship between StO2 in the injured and uninjured limb, and the presence of pre-operative vascular compromise was assessed. Seven out of 29 children presented with vascular compromise. Patients with clinical vascular compromise had significantly lower pre-reduction StO2 (63.5% ± 15%, mean ± standard deviation), compared to those without compromise (80.9% ± 10%). StO2 normalized following surgery in all children with vascular compromise. These improvements in muscle StO2 were associated, in all patients, with the clinical return of pulses and resolution of neurological symptoms if present. StO2 monitoring can identify patients with clinical vascular compromise, can identify the return of adequate perfusion following operative correction of supracondylar fractures, and may be a useful adjunct to clinical assessment.