A 3-mo-old male infant was referred to our hospital with micropenis. Since his serum LH, FSH, and testosterone levels were low (< 0.3 mIU/mL, 0.08 mIU/mL, and < 0.03 ng/mL, respectively), Kallmann syndrome/normosmic hypogonadotropic hypogonadism was suspected. In the process of searching for complications of Kallmann syndrome/normosmic hypogonadotropic hypogonadism, a right adrenal gland tumor was incidentally discovered. The patient was diagnosed with stage 1 neuroblastoma. A homozygous p.P147L (c.C440T) mutation in the KISS1R gene was detected as a cause of the congenital hypogonadotropic hypogonadism. KISS1-KISS1R signaling, which is essential for GnRH secretion, exhibits anti-metastatic and/or anti-tumoral roles in numerous cancers. High KISS1 expression levels reportedly predict better survival outcomes than low KISS1 expression levels in neuroblastoma. Therefore, decreased KISS1-KISS1R signaling may have played a role in the neuroblastoma in this patient.