Background: Kallmann syndrome is a rare genetic hormonal condition of hypogonadotropic hypogonadism with a prevalence of 1 in 4000-10000 live born. It is often associated with anosmia or hyposmia. To the best of the author’s knowledge, it has not been reported in Nigerian literature. Methodology: The patient had been presented at the Endocrine and Metabolic Unit of our hospital, and was thus managed. The patient’s hospital records were reviewed and relevant data were extracted, with investigation results and clinical pictures presented. Ethical approval was obtained from the Institution Ethics review board. Results: We report the case of a 15-year-old boy who was presented with a small sized penis since birth, with only a slight increment since then. His developmental milestones were reportedly normal but he had the inability to smell. Examination revealed a well grown apparently healthy looking male, weighing 40 kg; with a normal height of 151.5 cm and BMI of 17.5 kg/m2. The testes were 1 ml each in volume with a stretched penile length of 3.5 cm. Laboratory investigation revealed low testosterone, luteinizing hormone, and follicular stimulating hormone. His karyotype was 46XY. He was commenced on 200 mg monthly injection of testosterone to which he made significant improvement as his penile length increased to 8.5 cm over 8 months of therapy, pubic hair also developed to Tanner 3 but his testicular volume remained pre-pubertal. He also reported that he could now smell. Conclusion: Kallmann syndrome though a rarely reported condition in the Nigerian population, could be treatable, though attainment of reproductive capability might require further intervention. A high index of suspicion and early treatment may yield a better outcome.