Ethical dilemmas are multifaceted and complex, comprising a diverse set of viewpoints, values, beliefs, and attitudes. They rarely have a purely right or wrong answer. Not everyone will have the same answer to an ethical dilemma. Hence, teaching ethics is about helping students build critical thinking skills so that they can consider contradictory viewpoints to come out with the best course of action in the face of conflicting choices. Post pandemic, online teaching is now a norm. This study aims to explore the effectiveness of online debate in teaching ethics. Using Kialo Edu's free argument mapping and debate web tools in a synchronous online workshop, we conducted an undergraduate Ethics and Laboratory Safety module, where the students engaged in collaborative and real-time debates on an ethical statement. Feedback was collected through an anonymous online survey to evaluate the impact on student learning. The results showed a positive impact on their learning experience. This study highlights the potential of online synchronous debate in promoting active student participation and critical thinking in ethical dilemmas.