Calciphylaxis is a thrombotic vasculopathy characterized by painful necrotic ulcerations. There are no Food and Drug Administration approved therapies despite high mortality. To compare mortality and wound healing outcomes in patients treated with hyperbaric oxygen therapy (HBOT) in addition to intravenous sodium thiosulfate (IV STS) versus patients who received IV STS only. Findings were stratified by dialysis status and modality. 93 patients were included, with 57 patients in the control group (IV STS) and 36 patients in the treatment group (HBOT+IV STS). Mortality data were analyzed with traditional survival analyses and Cox proportional hazard models. Longitudinal wound outcomes were analyzed with mixed effects modeling. Univariate survival analyses showed that full HBOT treatment was associated with significantly (P=.016) longer survival time. Increasing number of HBOT sessions was associated with improved mortality outcomes, with 1, 5, 10 and 20 sessions yielding decreasing hazard ratios. There was also a significant (P=.042) positive association between increasing number of HBOT sessions and increased wound score. Data collection was retrospective. HBOT may have a role in the treatment of calciphylaxis with benefits demonstrated in both mortality and wound healing. Larger prospective studies are needed to identify which patients would most benefit from this intervention.