An Inquiry-based approach (IBA) is a teaching approach that promotes students' active learning and inquiry. This study examined the effectiveness of IBA as a tool for teaching Geography and explored the students' perceptions when they were taught using IBA. The investigation was carried out in one secondary school in Brunei Darussalam. A total of twenty students aged between 15 to 16 years old were selected as participants. This research adopted a qualitative approach using an action research. Data was collected from lesson observations, focus group interview, and achievement tests. The findings showed that there were remarkable improvements in the students' achievement tests. IBA successfully had helped students to develop some personal and inter-personal skills and encouraged them to become independent learners. However, there were some issues identified in this study. Obtaining information for their research was a challenge for many students, as they had limited access to computers and the Internet outside the school. The findings also revealed that the role of the teacher as the facilitator in IBA could be a challenge to the teacher herself.