Abstract: The study of seasonal influence on incidence of trunk borer infestation was undertaken during 2010 at Kapasia upazila under district of Gazipur, Bangladesh. The borer was found in orchard from June to September with a peak emergence in mid July. The larval population of Jackfruit trunk borer is the destructive pest stage, which evokes concern in jackfruit growing areas of Bangladesh. The highest percentage of infestation was in July (7.33%) followed by June and August (6.00%). The cumulative infestation over the year in the study area was 35.33% in October. The lowest infestation was observed in February (0.67%) whereas no activity was found during November to January. The incidence of infestation of trunk borer was influenced by temperature, rainfall and relative humidity due to seasonal variations and their contribution of the regression (R2) were 63, 65 and 31%, respectively. Five independent weather factors in stepwise regression equation pooled responsible for 67.4% of the total variance. Stepwise regression showed that maximum temperature was the most important to influence 35.3% and the influence was lowest (2.1%) in case of average rainfall.