The current study was conducted to see the effectiveness of using social media to enhance students' critical thinking skills. To fulfill the purpose of the study, a 14-week experimental study was performed with two groups of students. Both groups were introduced to how to respond to questions based on Revised Bloom's Taxonomy. During the period of doing the activity, students in the experimental group had to post answers in Facebook and got feedback from peers and teacher as mutual learning while those in the control group wrote their replies in papers and submitted them to the teacher in class. The research instruments used in this study included pre- and post-tests and a questionnaire. The data were analyzed by using dependent t-tests, independent t-tests, means, and standard deviations. After the experiment there was a difference in the mean scores of critical thinking ability between the two groups at the significance level of 0.05. The data obtained from the questionnaire manifested students' positive attitudes towards English instruction delivered through questioning technique and postings in Facebook.