Critical thinking (CT) is one of the important dimensions and goals of education which is expected of the students. It has been studied and reported that due to traditional teaching strategies, students think in ‘black and white’ (Dean, 2007) and rote memorisation has become part of our education system (Aly, 2007). Critical thinking requires an environment where students are engaged in different challenging and thoughtful tasks. There are different strategies to engage students in activities like; discussion, debate, reading, problem solving and enquiry. To study how enquiry-based teaching facilitates students’ CT, an action research was conducted with Grade VIII science students in Ibn-e-Sina Government High School, Karachi, as part of my M.Ed. course at AKU-IED. There were 32 students in the class and 26 of them willingly participated in this study. Pre and post interviews of five of the participants, one class observation and six teachings were the data collection steps of this study. The data revealed that the existing teaching practises in that class were more teacher-oriented which hindered students’ critical thinking. However, the data at the intervention stage indicates that enquiry facilitates CT of students by developing their skills of data collection and data evaluation, argumentation and questioning, and also shifting their attitude from teacher dependency to self-learning. It is important to provide students with opportunities to learn by experiencing and sharing their ideas fearlessly. This study data informs that enquiry enhances students’ autonomy to learn from each other and on their own. There is an intense need to shift the teaching and learning process from teacher centredness to learner centredness to make them critical thinkers, and enquiry is one of the most effective teaching and learning processes which ensures learners’ centrality. However, teachers’ CT and pedagogical skills are indispensable to implement enquiry-based teaching in real and large classrooms.