One of the consequences of the abuse in the use of antibiotics is the emergence of resistant bacteria, wich causes new drugs to be sought, and thus makes it necessary to seek alternatives sources. There are many natural compounds, obtained from cyanobacteria, that have an inhibitory effect against various pathogenic bacteria. In this group of cyanobacteria are those belonging to the Lyngbya and Pseudanabaena genera; therefore, the aim of this work was to evaluate the antibacterial activity of methanolic extracts from L. truncicola and Pseudanabaena sp. against reference strains: Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and Salmonella enterica ssp. enterica serovar Typhimurium. The cyanobacteria were propagated in BG-11 medium with constant aeration and a 12 hour light: dark photoperiod. The antibacterial activity test was carried out by the Kirby-Bauer method. The antibacterial effect was observed as growth inhibition halos. All the microorganisms presented suffered inhibition, the greater effect was produced on S. enterica ssp. enterica serovar Typhimurium. The largest halos were obtained with the extract of Lyngbya truncicola.