Puberty is the transitional period between childhood and adulthood, a process encompassing morphological, physiological and behavioural development to attain full reproductive capability. This study aimed to assess serum relaxin-3 hormone relationship with male delayed puberty. Sixty males were investigated as two equal groups: males with delayed puberty and healthy matched males as controls. They were subjected to history taking, clinical examination and estimation of serum FSH, LH, testosterone, relaxin-3 hormonal levels. The results showed that the secondary sexual characters in the patients group were at Tanner stages 1-2 and in the healthy controls at Tanner stages 3-5. The mean BMI in the patients group was significantly increased, whereas the mean levels of the span, testicular volume, serum LH, FSH, testosterone as well as relaxin-3 hormonal levels were significantly decreased compared with the healthy controls. Serum relaxin-3 levels showed significant positive correlation with the age, testis volume, span, Tanner stages, serum testosterone, FSH, LH hormones. In addition, serum relaxin-3 levels showed significant negative correlation with BMI. It is concluded that serum level of relaxin-3 hormone is an important mediator in the pathophysiological process of normal puberty being significantly decreased in males with delayed puberty.