Abstract The present research aimed at enhancing university students' critical writing and reflective thinking skills. This was achieved through applying a Collaborative Research-Based ESP Program. The research adopted two groups design with pre/post-test treatment. The sample consisted of 50 students. The following instruments were designed and used: A Critical Writing Skills Checklist (CWSC); A Critical Writing Skills Pre/Post Test (CWST); A Reflective Thinking Questionnaire (RTQ) and a Reflective Thinking Skills Pre/Post Test (RTST). Results of the research indicated that there were statistically significant differences at 0.05 level between the mean scores of the experimental group on the pre/post administrations of the pre/post-tests, the CWST and the RTST, in favour of the post ones. In addition, the experimental group students outperformed their counterparts in the control group students in the target skills. Consequently, the proposed Collaborative Research-Based ESP Program proved to be effective in developing critical writing and reflective thinking skills for university students. Keywords: Differentiated Instruction, Multiple Intelligences, Critical Reading Skills.