Although the accumulation of pharmaceutical drugs in aquatic bodies has increased rapidly in recent years, the effect of rifampicin (RIF), a first-line anti-tuberculosis drug, on fish feeding, growth, and embryonic development is unknown. This investigation aimed to determine the impact of RIF on growth and embryonic developmental profile in the mosquitofish Gambusia affinis. Experimental groups included controls, which were kept in normal water for 21 days, whereas those in the second, third, and fourth groups were exposed to 50, 200, and 500 mg RIF/L water, respectively. The food intake rate and Specific Growth Rate (SGR) showed a concentration-dependent significant decrease in RIF-treated fish compared with controls, and a strong positive correlation was found between food consumption and SGR. A significant decrease in the number of embryos at an early stage of development and the total number of embryos in RIF-treated fish was associated with several congenital anomalies such as lack of vitellogenin accumulation, yolk sac regression, decreased pigmentation, aggregations of blood vessels, and curvature of the spinal cord compared with controls. Together, these results reveal for the first time that RIF treatment not only impacts feeding and growth, but also exerts potential teratogenic effect on embryonic developmental stages in the mosquitofish G. affinis.