This study aimed to evaluate the potential beneficial effects of SCFAs, used as a feed additive, on intestinal microbiota composition. For this purpose, a specific combination of short and medium chain fatty acids was tested in juvenile gilthead sea bream (Sparus aurata) fed a plant-based diet. The Illumina MiSeq platform for high-throughput amplicon sequencing of 16S rRNA gene, and QIIME pipeline were used to analyse and characterize the whole microbiome associated to both, feeds and S.aurata intestine. In summary our findings clearly indicated that SCFAs positively modulated the fish intestinal microbiota by increasing the number of beneficial lactic acid bacteria, namely Lactobacillus, and reducing Gammaproteobacteria that include several potential pathogenic bacteria.