Abstract: The present study aimed to determine the effect of testosterone undecanoate hormone on sperm quality (sperm viability) and sperm quantity (sperm counts) and its levels in the hemolymph of male mud spiny lobster, Panulirus polyphagus. Male P. polyphagus was injected laterally in fifth abdominal segment of pure hormone, Testosterone Undecanoate (TU) and ethanol at days 1, 8, 15, 22 and 29. Hemolymph of P. polyphagus was taken every two weeks and checked with Enzyme-linked immunosorbent assay (ELISA) to measure hormone levels. The mean sperm quality and quantity were increased due to increase the TU dose and TU levels also increase. The sperm quality, quantity and hormone levels were relevance each others. These findings indicate that TU injection should be evaluated as a practical way of improving sperm quality and quantity in commercial operations.