Mutilated hand injuries are a profound challenge to the plastic surgeon, and such injuries often lead to limb loss and severe functional impairment. Hyperbaric oxygen therapy (HBOT) appears to counteract tissue hypoxia and stimulate acute wound healing. This study was performed to evaluate the efficacy of HBOT as an adjunctive therapy in patients with a mutilated hand injury. Between January 2006 and December 2014, 45 patients with a mutilated hand injury were enrolled. After reconstruction or revascularisation, patients underwent 120 minutes of HBOT with oxygen at 2·5 atmospheres absolute while breathing 100% oxygen. Outcomes such as amputee survival and surgery-related complications were recorded. The patients were 38 men and 7 women with average age of 37·2 years (range 18-62). The mean defect area was 131·5 cm(2) (range 40-300). Most patients experienced a pure crush injury (53%). The average number of operations from the initial debridement to the first reconstruction was 3·8 (range 1-6). A total of 33 patients (73%) underwent replantation during the initial reconstruction. For flap coverage, most patients received a free flap using an anterolateral thigh flap (18 patients) or local flap using an abdomen/groin flap (nine patients). The average time from the first reconstruction or revascularisation to the first HBOT was 6·5 hours (range 2-12). The average number of HBOT sessions was 9·1 (range 6-14 sessions). The survival rate of the replanted fingers was 81%, and the survival rate of the palms was 100%. Most complications in the initial reconstruction involved partial loss of an avulsed flap, and most complications in the chronic stage (≥3 months) involved scar contracture. When combined with delicate microsurgery, early intervention using adjunctive HBOT was effective in preserving partially viable tissue and restoring hand function in patients with a mutilated hand injury.