Background Gastrointestinal cancers are the most dangerous cancers all over the world. The gut microbiota dysbiosis increases the risk of GI cancers and induces the host’s susceptibility to carcinogenic bacteria. Antibiotic resistance is rising in these bacteria. Thus, discovering new safe and effective antibacterial agents is a worldwide concern. This study evaluates the antibacterial activity of six wild medicinal plants from the Al Bahah region in Saudi Arabia. Methods Arial parts of Cissus quadrangularis, Aloe castellorum, Psiadia punctulata, Aloe pseudorubroviolacea, Barbeya oleoides, Teucrium yemense were collected and dried for extraction with ethanol. The minimum inhibitory concentrations (MIC) of these ethanolic extracts against carcinogenic bacteria Bacteroides fragilis, Clostridium ssp., Cutibacterium acnes, Escherichia coli, Fusobacterium nucleatum, Helicobacter pylori, Mycoplasma spp., Neisseria gonorrhoeae, Porphyromonas gingivalis, Salmonella enterica, and Treponema pallidum were evaluated to determine its antibacterial activity. Results All extracts showed antibacterial activity with MIC lower than 1 mg/ml. Psiadia punctulata showed higher antibacterial activity, while the Aloe species showed the lowest antibacterial activity. Conclusion The studied plants’ extracts showed high effectiveness as antibacterial activity against the carcinogenic bacteria related to gastrointestinal cancers due to their high content of pharmaceutical components. These plants could be explored further for the development of new antibacterial products against these carcinogenic bacteria.