Jackfruit (Artocarpus heterophyllus) root extract, with a bronchodilating agent, is traditionally used for treating asthma. To provide a scientific basis for such claim, this study was conducted to evaluate the safety and efficacy of the formulated syrup of such extract by determining its acute oral toxicity level, approximate effective dose, the significant difference in the total leukocyte count (TLC), total eosinophil count (TEC) and histopathologic evaluation of lung tissue. Female Swiss mice were used to determine the toxicity at selected fixed dose levels of 5, 50, 300 and 2000 mg/kg. Approximate Effective Dose (AED) determination was conducted using female albino rats with a logarithmic increase by 0.6 intervals. Animals were administered with alum-ovalbumin and desired dose of root extract, respectively. Blood samples were collected for leukocyte and eosinophil counts. It was found that acute oral toxicity was at 2000mg/kg and 5000 mg/kg. AED has significant influence on TLC and TEC at dose levels of 15.85, 251.19, 1000 and 3981.07 mg/kg. Analysis of Variance showed a significant difference in the mean of the decrease in the total leukocyte count due to the formulated syrup of root extract, Salbutamol (positive control) and plain syrup (negative control). Tukey’s multiple comparison tests, t-test and histopathologic evaluation on the group treated with Salbutamol and root extract formulation showed no significant difference on the TLC and TEC. Salbutamol was not significantly different from the formulated syrup. Hence, both treatments were effective as bronchodilating agents.