Diarrhoea remains a main public health concern, especially in rural as well as indigenous populations due to lack of modern medical access. The Santhal tribe of Mayurbhanj district in Odisha, India, possesses widespread traditional knowledge of using local medicinal plants for treating diarrhoeal conditions. This traditional exercise reflects their long-standing relationship with the natural environment and its curative potential. An ethnobotanical field study was conducted from 2022–24 to document and analyse the antidiarrhoeal plant knowledge among the Santhal community at Mayurbhanj. Information was gathered from 95 informants through semi-structured interviews and focused group discussions. The significance of each species was assessed using quantitative indices such as the relative frequency of citation (RFC) and use value (UV). The study recognised 37 medicinal plant species from 24 botanical families used traditionally for diarrhoea treatment. Among these, Punica granatum L. (RFC = 0.86), Tamarindus indica L. (RFC = 0.76) and Diospyros melanoxylon Roxb. (RFC = 0.60) were the most mentioned. Various preparation methods were reported, including juicing, grinding into paste, maceration, burning and direct chewing of plant parts. The ethnomedicinal practices of the Santhal community highlight the importance of traditional knowledge systems in primary healthcare. These findings call for further scientific validation of the noted species to assess their therapeutic potential and safety through phytochemical and pharmacological research.