This study aimed to investigate the effectiveness of a training program using some cognitive strategies on improving Writing Self-Efficacy in English among the 11th grade students in the Sultanate of Oman. The study sample consisted of 50 students from the 11th grade in Muscat Governorate. They were divided into two groups, an experimental group which consisted of (25) students, cognitive strategies in writing: planning, editing and revision were applied to this group, and a control group which consisted of (25) students and they were not given any of these strategies. The study lasted for (approximately 6 weeks) during the second semester of the academic year 2017/2018. To achieve the aims of the study, the pre and post administration of Writing Self Efficacy Scale was administered for the experimental and control groups. The following statistical tools were used: means, standard deviations, independent sample t-test and paired sample t-test. The results showed statistically significant differences between the mean scores of the experimental and control groups in the post-admimistration of the writing self efficacy Scale in total score and in all its dimensions (conceptual, operational and self regulation) in favor of the experimental group. The results also showed statistically significant differences between the mean scores of the experimental group in the pre and post adminstration of writing self-efficacy Scale in total score and in all its dimensions (conceptual, operational and self-regulation) in favor of the post-adminstration, which indicates that Writing Self-Efficacy has improved after the adminstartion of the training program, Keywords: Cognitive strategies, Writing Self-Efficacy, a Training program