The use of brewer’s yeast at probiotic levels (up to 2%) has proven to have a positive effects on the performance and welfare in several fish species, such as African catfish Clarias gariepinus [5] and hybrid striped bass Morone chrysops × M. saxatilis [6]. However, in studies where brewer’s yeast was tested as protein source, i.e., when high levels are required, the results are not entirely clear. Rainbow trout (Oncorhynchus mykiss) and tilapia (Oreochromis niloticus) fed with diets containing moderate to high yeast levels were reported to have reduced feed intake and growth, reduced liver glycogen and increased total liver lipids [7–10]. Conversely, the inclusion of 30–50% brewers yeast in the diet improved feed efficiency of European seabass [11] and Pacu, Piaractus mesopotamicus [12]. The aim of this study was to investigate the effects of partial and total fishmeal replacement by brewer’s yeast on growth, body composition, feed utilization and digestibility of juvenile tilapia