This study has investigated the effects of folic acid on the reproductive efficiency and health of the Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). The adult broodstock fish were fed commercial diets (36% crude protein) supplemented with different graded levels of folic acid (2.5, 5.0, and 7.5mg/ kg diet) in addition to the fourth control group of un-supplemented feed. Fish were stocked in separate hapas widened in four concrete ponds over three months. At the end of the experiment, blood samples were collected from each fish and the following parameters were estimated calorimetrically in blood serum: aminotransferases (AST and ALT), glucose and urea, protein, creatinine, and finally albumin and globulins. However, the histological investigations of the liver and gonads (testes and ovaries) were done and described using histological techniques of hematoxylin and eosin staining, and then the sections were analyzed and photo-documented by using an Olympus BX50 microscope. It was found that folic acid increased the total blood protein, albumin, globulins, and estradiol levels but suppressed blood ALT and AST activities and urea and creatinine levels in the adult Nile tilapia. Dietary folic acid (Vitamin B9) also plays a crucial role in enhancing reproductive performance since higher nutritional levels of folic acid significantly improved the fertility of fish males and females. It positively affected fish gonads histology with notable improvements. Additionally, the present study demonstrated non-significant adverse effects on fish blood biochemical and aminotransferases at moderate levels of supplemented folic acid. The current study suggested folic acid safety and efficacy as a dietary additive for fish well-being and good reproductive performance. The results advocate further exploring dietary folic acid in fish farming practices to optimize growth and reproductive health.