In order to understand the seasonal occurrence and activity of insect pest on cotton, studies were carried out at Cotton Research Institute, AARI, Faisalabad during 2009. On June 30, 2009, maximum thrips (31±1.15/leaf), mites population (35.33±2.72/leaf) was recorded and whitefly (21.33±2.85/leaf) was recorded during the whole month of August but abundant population of jassid (3.33±0.33/leaf) was during October. In general three months viz., May, June and July boosted Thrips and mites population beyond the economic threshold level (ETL). Jassid and whitefly population remained above ETL throughout observation period except during April when its activity was comparatively lower. It was concluded that last two weeks of June were the most favorable for thrips and mites population and whole month of august and September encouraged jassid, whitefly and mealybug population. It was further concluded that transgenic cotton had no impact against population build up of sucking insect pest of cotton.