The leaf-cutting ant, Atta mexicana Smith, is a pest commonly managed by synthetic insecticides. Considering negative environmental and health impacts produced by insecticides, alternative strategies such as plant-derived insecticides are an option for controlling the ant. Effects of 20 serial dilutions of refined azadirachtin oil and three post-exposure times were assessed on A. mexicana forage workers in a laboratory. The dilutions were applied directly to ants. Azadirachtin concentration and post-exposure time significantly affected mortality of A. mexicana. The mean lethal concentration at 0 hours post-exposure was 2.26 × 10¹ mg/ liter and at 50 and 100 hours was 1.67 × 10^-6 mg/ liter and 1.65 × 10^-14mg/ liter, respectively. Findings on toxicity of azadirachtin to A. mexicana are of great importance for pest management strategies in agriculture. Insecticides based on azadirachtin oil should be considered among integrated pest management strategies recommended by the Plant Health Commission in the Americas.