Terrestrial invertebrates are subjected to a wide range of microbial infections throughout their life. Therefore, they have powerful antimicrobial agents. The present study was designed to evaluate the antibacterial efficiency of different extracts of terrestrial gastropods against two pathogenic bacteria: Escherichia coli and Staphylococcus aureus. Phosphate buffer saline (PBS), acetone, and methanol were used to extract viscera, haemolymph, and mucus from the snails, Helix aspersa and Eobania vermiculata, and the slug, Deroceras reticulatum. All extracts from haemolymph and mucus of the three snails did not inhibit the growth of the selected pathogenic bacteria. However, the methanolic extract of E. vermiculata viscera inhibited the growth of S. aureus at 50% concentration; and the inhibition zone reached 12.3 ± 0.6 mm. In addition, the methanolic extract of H. aspersa viscera inhibited the growth of S. aureus at 100 and 50% concentrations up to 19.3 ± 0.6 and 18.0 ± 0.1 mm, respectively, and induced a moderate decrease in the growth of E. coli at 100% concentration. In addition, scanning electron microscopy (SEM) assured damaging impacts of the methanolic and PBS viscera extracts of the two snails “H. aspersa and E. vermiculata" on both E. coli and S. aureus. In conclusion, the antibacterial properties of the methanolic viscera extracts of the terrestrial gastropods may encourage the discovery of new and safe antibiotics from animal origin.