This study aimed at investigating the effectiveness of Collaborative Strategic Reading (CSR) in developing reading comprehension skills of EFL secondary stage students. Two intact classes of second year secondary stage students from Belqas Al-Azhar Secondary Institute for Girls participated in this study. One class (N= 30) was assigned as the experimental group and received CSR instruction. The other class (N= 30) was assigned as the control group and received regular instruction of reading comprehension. The treatment lasted for 12 weeks. To collect data, a pre-post reading comprehension skills test was used to assess the EFL students' reading comprehension skills before and after the treatment. T-Tests and Eta-square (η2) were used to analyze the data statistically. Results showed that there is a statistically significant difference at the 0.01 level between the mean score of the experimental group students and that of the control group on the post-administration of the reading comprehension test in favor of experimental group students. Based on the findings of this study, it could be concluded that CSR had a positive effect on developing secondary stage students' reading comprehension skills and was more effective in developing critical comprehension skills than inferential or literal comprehension skills. Keywords: Collaborative Strategic Reading (CSR), reading comprehension skills, EFL