Excessive application of antibiotics to control fish and shrimp diseases in aquaculture has been associated with several drawbacks, such as immune suppression, development of antibiotic-resistant bacterial strains, and elevated levels of antibiotic residues in animal products. To overcome this problem and to promote fish health and their productivity, several immunostimulants have been used as additives in aquafeeds. In this regard, interest in the research on the use of short-chain fatty acids (SCFA) in aquafeeds is increasing tremendously, as they exert several beneficial effects on farmed fish and shrimp. Among SCFA, butyric acid (BA); its salts, such as sodium butyrate (SB); and their protected forms have attracted particular attention of researchers as growth promoters and immunostimulants as well as for their antioxidant properties. Until date, extensive studies have been conducted on the beneficial effects of BA, SB, and their protected forms on growth performance, feed utilization, proximate body composition, intestinal health status (gut microbial communities, the histo-morphological structure of the intestinal villi, and digestive enzymes), antioxidant properties, haemato-immunological functions, expression of immune genes and pro-inflammatory cytokines, and resistance of fish and shrimp to diseases. These studies have demonstrated SCFA as promising feed additives in aquaculture. The present review article summarizes the beneficial effects of dietary supplementation of BA, SB, and their protected forms on aquatic organisms. Furthermore, the review discusses the information available pertaining to their modes of action.