This study aimed to investigate the effectiveness of an online collaborative learning program based on the cognitive apprenticeship model to develop student teachers' EFL argumentative writing and critical thinking skills. The study used a pre-post experimental one-group design. The participants were 45 third-year English students enrolled in the English section at the Faculty of Education, Benha University. The study instruments included an EFL argumentative writing skills test and an EFL critical thinking skills test. Students were pre-tested to measure their level of argumentative writing and critical thinking skills. Then, they underwent training via the online collaborative learning and cognitive apprenticeship model to develop their argumentative writing and critical thinking skills. The training encompassed six phases of the program: modeling, coaching, scaffolding, articulation, reflection, and exploration. Students were post-tested at the end of the intervention to assess the progress in their level of performance in EFL argumentative writing skills and critical thinking skills. The results demonstrated a statistically significant difference between the mean scores of the study participants in the pre- and post-administrations of the EFL argumentative writing skills test and the critical thinking skills test in favor of the post-administration. Therefore, it could be concluded that participation in online collaborative learning activities based on cognitive apprenticeship theory greatly enhanced student teachers' EFL argumentative writing and critical thinking abilities.