An adult, wild-caught, intact female Aubry's flapshell turtle (Cycloderma aubryi), that had been in the collection for 21 months, presented with rapid onset of multifocal, tan-white, 1.5 cm and smaller, crateriform, ulcerated lesions on the carapace and plastron. Empirical antibiotic therapy, initiated on the suspicion of an infectious etiology, yielded no clinical improvement and the disease progressed. Multifocal osteomyelitis was visible deep to the dermatological lesions on the carapace and plastron on computed tomography (CT) imaging, and culture results included Stenotrophomonas maltophilia and Achromobacter (Alcaligenes) xylosoxidans. Two months after surgical debridement and ostectomy, healing of lesions was incomplete and slow to progress. Photobiomodulation (PBM) was initiated on some of the lesions, and the treated lesions showed grossly visible indications of progressive healing after 17 days; there were no indications of healing in the untreated lesions. All lesions were subsequently treated with PBM, and the patient made a full recovery. This case report describes successful treatment of severe ulcerative dermatitis in a softshell turtle using advanced imaging (CT), surgical debridement and ostectomy, supportive care, husbandry modifications, and PBM. This report highlights that PBM can be a valuable therapeutic tool that should be considered for treatment of ulcerative dermatitis in softshell turtles, especially in patients with delayed wound healing or chronic dermatologic lesions.