Neurological complications during critical illness remain a frequent cause of morbidity and mortality. To date, monitors of cerebral function including electroencephalography, jugular bulb mixed venous oxygen saturation and transcranial Doppler, either require an invasive procedure and/or are not sensitive enough to effectively identify patients at risk for cerebral hypoxia. Near-infrared spectroscopy is a noninvasive device that uses infrared light, a technique similar to pulse oximetry, to penetrate living tissue and estimate brain tissue oxygenation by measuring the absorption of infrared light by tissue chromophores. The following article reviews the latest technology available to monitor cerebral oxygenation, near-infrared spectroscopy, its advantages and disadvantages, the currently available evidence-based medicine that demonstrates that this technology can identify deficits in cerebral oxygenation, and that monitoring such deficits allows for therapy to reverse cerebral oxygenation issues and thereby prevent long-term neurological sequelae.