Thisis the first case report in Oman and the Gulf region of a 17-beta-hydroxysteroid dehydrogenase type 3 [17-beta-HSD3] deficiency with a novel mutation in the HSD17B3 gene that has not been previously described in the medical literature. An Omani child was diagnosed with 17-beta-HSD3 deficiency and was followed up for 11 years at the Pediatric Endocrinology Clinic, Royal Hospital, Oman. He presented at the age of six weeks with ambiguous genitalia, stretched penile and bilateral undescended testes. Ultrasound showed no evidence of any uterine or ovarian structures with oval shaped solid structures in both inguinal regions that were confirmed by histology to be testicular tissues with immature seminiferous tubules only. The diagnosis was made by demonstrating low serum testosterone and high androstenedione, estrone, and androstenedione: testosterone ratio. Karyotyping confirmed 46, XY and the infant was raised as male. Testosterone injections [25 mg once monthly] were given at two and six months and then three months before his surgeries at five and seven years of age when he underwent multiple operations for orchidopexy and hypospadias correction. At the age of 10 years he developed bilateral gynecomastia [stage 4] . Laboratory investigations showed raised follicle-stimulating hormone, luteinizing hormone, androstenedione, and estrone with low-normal testosterone and low androstendiol glucurunide. Testosterone injections [50 mg once monthly for six months] were given that resulted in significant reduction in his gynecomastia. Molecular analysis revealed a previously unreported homozygous variant in exon eight of the HSD17B3 gene [NM_000197.1: c.576G>A. Trp192*] . This variant creates a premature stop codon, which is very likely to result in a truncated protein or loss of protein production. This is the first report in the medical literature of this novel HSD17B3 gene mutation. A literature review was conducted to identify the previous studies related to this disorder