Serotonin (5-HT) has been proven to stimulate ovary maturation of crustaceans. Herein, we hypothesize that supplementary dietary tryptophan (TRP), a precursor of 5-HT, could be an easy and effective approach to stimulate ovary maturation in female tiger prawn Penaeus monodon broodstocks by enhancing serotonergic activity of central nervous system. The effects of TRP-supplemented diets (0.25, 0.5, and 1% of dry diet) on ovary development were evaluated in a five-week period. Most of the ovary in the prawn advanced toward the developing stage (Stage II). The gondosomatic indexes in the prawn fed with the feed with 1% of TRP-supplemented diets significantly differ from the control group. It showed that TRP did stimulate ovary developing in tiger prawn but might need more time to complete the goal in stimulating ovary maturation.