Ethnomedicine using mostly plants is of pivotal importance nowadays in several Transylvanian regions in Romania. In this study (2007–2015), one Swabian-German, one Hungarian, three Csángó-Hungarian and nine Székely-Hungarian villages were selected to collect ethnomedicinal treatments for various gastrointestinal diseases. Some of the studied villages have partial or no permanent medical and pharmaceutical services. The 374 inhabitants interviewed used mostly medicinal plants based on ancient knowledge. The 78 (53 wild and 25 cultivated) plants documented have 181 local names and are used to treat ailments such as loss of appetite, bloating, stomach ache, gastric ulcer, and diarrhea, mostly in tea form. This knowledge decreases continuously because of loss of interest among young people and through frequent use of media sources and books. Although some of these plants have also been described in official medicinal sources, several data suggest the need for further fieldwork and new experimental analyses to highlight the valuable role of these plants in recent phytotherapy.