Resumen. Se evaluó un extracto de ajo (EA) para inducir la defensa de plantas de tomate contra Fusarium oxysporum radicis-lycopersici (Forl), mediante el incremento de la concentración endógena de ácido salicílico (AS) y ácido jasmónico (AJ). La aspersión de 1 y 2 % del EA sobre plantas intencionalmente infectadas con 1x10 7 esporas mL -1 de Forl, redujeron en 73.53% la severidad de la enfermedad producida por Forl respecto al control infectado. La altura fue similar (p≤0.05) en plantas tratadas con EA y no-tratadas. Abstract. A garlic extract (EA) was evaluated to induce the defense of tomato plants againstFusarium oxysporum radicis-lycopersici (Forl), by increasing the endogenous concentration of salicylic acid (AS) and jasmonic acid (AJ). Spraying 1 and 2% of EA on plants intentionally infected with 1x10 7 spores.mL -1 of Forl reduced in 73.53% the severity of the disease produced by Forl with respect to the infected control. The height was similar (p≤0.05) in plants treated with EA and untreated. The accumulation of AS in plants spayed with 1 and 2% of EA presented two significant increases (p≤0.05), in the second and fifth weeks after spraying, with higher concentrations than the infected and non-infected controls in 11 and 6 times for the first and 2.7 times and 3.8 times for the second, respectively. The AJ was induced from the first week after the treatments, increasing 2.5 and 1.8 times more than the infected and non-infected controls, maintaining those values throughout the evaluation. The results show that the EA reduced the development of the disease caused by Forl Publicación en línea, septiembre 2018 395Fully Bilingual Revista Mexicana de FITOPATOLOGÍA Mexican Journal of Phytopathology