Abstract The objective this study was to obtain extracts, using ultrasound and enzymes, of leaves of Psidium. cattleianum Sabine, collected in the summer and winter, and evaluate the antioxidant, allelopathic and antimicrobial activities. Photomicrographs of leaf structure were obtained by SEM. The phenolic compounds content (TPC) and the antioxidant activity were determined. The allelopathic activity was verified in bioassays for each of the extracts against the test plant (Lactuca sativa). The antimicrobial activity was determined against Gram-positive and Gram-negative bacterial species. It was evaluated the use of extracts as disinfectants. The SEM showed that the extraction form affected the cell structure of the leaves but did not influence the TPC. The highest TPC was found in leaf extracts collected during winter, with values between 123 and 144 mg EAG.g−1. The level of antioxidant activity estimated presented higher value for the leaves collected in the summer, where the IC50 presented values of 37 μg mL−1. The results also indicate that all extracts tested show considerable allelopathic activity, with inhibition of growth of more than 50%. The antimicrobial activity can be classified as partially active to very active, where the best results were found against L. monocytogenes, with inhibition halos measuring up to 23 mm. It was also verified that the time of collection of leaves interfered in the values found. With regard to surface disinfection, all the extracts tested positive results. Experiments have shown that extracts of P. cattleianum Sabine are a source of bioactive compounds, which have antioxidant, allelopathic and antibacterial activity.