Abstract The present study aimed at investigating the impact of an online annotation tools-based program on enhancing EFL secondary stage Students' in critical writing skills. The instruments that were designed and used in the current study were a critical writing skills questionnaire and a pre-post Critical writing skills Test for assessing Secondary Stage Students' Critical writing skills before and after receiving the program. The study adopted the quasi-experimental design using experimental and control groups. Participants were consisted of sixty students randomly selected from first year secondary stage of Monshaat Al Salam Secondary School, Mansoura, Dakahlia governorate during the first semester of the academic year 2021-2022. The participants were taught using online annotation tools-based program. Results provided evidence to the effectiveness of using Online Annotation Tools Based program in improving the students' Critical writing skills. A number of recommendations concerning the use of Online Annotation Tools Based program. Key words: Online Annotation Tools, Critical Writing Skills, Secondary Stage Students