Ulcerative colitis (UC) is a chronic, nonspecific, relapsing inflammatory bowel disease. Metformin has pleiotropic effects including anti-inflammatory properties and a notable impact on the gut microbiome. gammadeltaT17 cells play crucial role in initiating and maintaining intestinal inflammation. The effect of metformin on gammadeltaT17 cells remains unclear. This study aims to explore the connection between metformin-mediated ameliorated response in colitis mice and gammadeltaT17 cell activity. The role of gammadeltaT17 cell inhibition in metformin-mediated colitis amelioration was evaluated in mice. The effect of metformin on gammadeltaT17 differentiation and the possible mechanism were evaluated in a set of in vitro experiments. Results showed that the accumulation of gammadeltaT17 cells was negatively correlated with metformin treatment in DSS-induced colitis mice. Exogenous gammadeltaT17 cells blocked metformin-mediated colitis inhibition. Furthermore, metformin inhibited gammadeltaT17 differentiation, which was related to the inhibition of mTOR/RORgammat activity. Our results reveal that metformin ameliorates colitis symptoms by suppressing gammadeltaT17 differentiation, suggesting a viable strategy against UC, although the mechanism of metformin in inhibiting gammadeltaT17 differentiation remains to be further studied.