Lycopersicon esculentum (tomato) fruit is a widely studied matrix. However, only few works focus their attention on its seeds, which constitute a major byproduct of the tomato processing industry. In this study the antimicrobial potential of ten different tomato seed extracts from "Bull's heart" and "Cherry" varieties were analyzed against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Enterococcus faecalis and Bacillus cereus) and Gram-negative (Proteus mirabilis, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium) bacteria and fungi (Candida albicans, Aspergillus fumigatus and Trichophyton rubrum). Regarding antibacterial capacity, the different extracts were revealed to be active only against Gram-positive bacteria, E. faecalis being the most susceptible one (MIC: 2.5-10 mg/mL). Concerning antifungal activity, "Bull's heart" extracts were the most active. In a general way C. albicans was the most susceptible species (MIC: 5-10 mg/mL). The chemical composition of the extracts was also pursued, concerning organic acids, phenolics and fatty acids, in order to establish a possible relationship with the observed antimicrobial effect.