The present work was carried out to study the effect of manual topping of cotton plants at different ages, on the infestation levels of bollworms (Pectinophora gossypiella (Saund.) and Earias insulana (Boisd.)) and produced cotton yield. All trials were conducted at a private farm, El Azizia village, Minia Al-Kamh district, Sharkia Governorate, Egypt during 2021 and 2022 seasons. Three main treatments of topping cotton plants were conducted, each main treatment including sub-treatments. Results revealed that all treatments of plants topping at different ages had achieved significant increase in the produced mature bolls per plant, highly significant decrease of bollworms infestation and significant increase of boll weight and total yield per plant as compared to the same parameters in un-topped plants. Results also demonstrated that the highest number of produced bolls per plant, reduction of bollworms infestation and increase of yield per plant were achieved in the topped plants three times at age between 120 and 140 days.