Hyperbaric oxygen therapy (HBO) is the inhalation of 100% oxygen inside a hyperbaric chamber pressurized to greater than 1 atmosphere. This treatment has been approved for use in several indications including decompression sickness, carbon monoxide poisoning, severe burns, and chronic infections. HBO has been studied in cerebral palsy (CP), based primarily on the concept of improving oxygen availability to damaged brain cells with potential for recovery, even after chronic injury. The evidence on HBO in CP is limited by imprecision and control groups with methodological flaws. Observational before-after studies stimulate the interest in HBO for CP but are limited by methodological risk of bias. Adverse events of HBO include middle-ear barotrauma, often requiring myringotomy and tube placement, and a potential increased risk of seizures. The use of HBO in CP remains controversial. In all these fields, the hyperbaric oxygen therapy is reviewed.