The goal of this study was to assess the antimicrobial activity of the essential oil and aqueous, alcoholic, and ethyl acetate extracts of Guarea kunthiana A. Juss against ten Salmonella serotypes from poultry origin (Enteritidis, Infantis, Typhimurium, Heidelberg, Mbandaka, Give, Saintpaul, Ohio, Gallinarum, and Agona); the insecticidal potential of the oil and extracts against larvae and adults of Alphitobius diaperinus (Coleoptera: Tenebrionidae) (Panzer, 1797); and also to determine the antioxidant activity of these compounds using the capture method of radical 2.2-diphenyl-2-picrylhydrazyl (DPPH). With respect to the antimicrobial activity of the essential oil of G. kunthiana, the most sensitive serotypes were Infantis, Typhimurium, and Give, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 54.6 µg/ml. Regarding the other serotypes tested, the action of the oil was classified as moderate, weak, or inactive. With respect to the extracts, the greatest microbial susceptibility was observed in the activity of the alcoholic extract, with MIC and MBC values of 0.39 mg/ml for the serotype Infantis, and MIC and MBC values of 0.78 mg/ml for the serotype Gallinarum. The results of the insecticidal activity of the essential oil and the extracts were found to be low, with 28% mortality of larvae and 12% of adults, at a concentration of 200 mg/ml. Regarding the extracts, the best results were observed using the alcoholic extract at concentrations of 10%, with 34 and 44% mortality of larvae and adults, respectively. The values of antioxidant activity showed that there were no significant differences between the synthetic antioxidant butylhydroxytoluene (BHT), the essential oil, and the alcoholic extract, revealing that both the essential oil and the alcoholic extract of G. kunthiana exhibited high antioxidant capacity.