Equine gastric ulcer syndrome (EGUS) is the most common disease of the equine stomach with high prevalence of both squamous and glandular disease reported in various populations. The aim of this study was to evaluate the effectiveness of a phytotherapic compound (pHhyloGASTRO) in the therapy of EGUS. The study was performed as a randomized double-blinded single-center study. The study population was composed of 19 equids which were submitted to gastroscopy before and after a 6-week treatment with feed additive (10/19) (pHyloGASTRO, 4Union B.I.O. srl, Italy) or a placebo (9/19). Severity grade was evaluated on a scale from 0 to 4. The variables of interest were gastric lesion score and improvement grade. Changes and comparisons of variables were performed by contingency table analyses. P level of significance was set at .05 in all analyses. In terms of gastric lesion scores, the treated group improved significantly compared to the placebo group. pHyloGASTRO seems to be effective in the treatment of EGUS. Further studies are needed to verify whether prolonged administration of pHyloGASTRO could be more effective in completely healing gastric lesions.