The present study aimed at investigating the effectiveness of an online program based on inquiry cycle based jigsaw (ICBJ) for developing EFL 4^th year student teachers' critical reading skills. One instrument was developed for the purpose of this study; a pre-post critical reading skills test. The participants of the study consisted of sixty students selected randomly from EFL 4^th year student teachers at Faculty of Education, Damietta University in the academic year 2020/2021. The study adopted the quasi-experimental research design. Therefore, the participants were randomly assigned into two groups: an experimental group (n=30) and a control one (n=30). The experimental group received training through the proposed program based on an online inquiry cycle based jigsaw (OICBJ). On the other hand, the control group received instruction through the regular method. Participants were pre- and post-tested on the instrument: the EFL critical reading skills test (CRST).  Results revealed that the experimental group outperformed the control group in the post administration of the EFL critical reading skills test. The study concluded that the online program based on an online inquiry cycle based jigsaw (OICBJ) enhanced EFL 4^th year student teachers' critical reading skills. A number of recommendations and suggestions for further studies were presented.