This project aims to promote critical thinking skills in intermediate English level learners through the application of problem solving tasks. The main goal is to show the extent to which problem solving tasks promote critical thinking, and to identify the type of tasks that work best to promote critical thinking. This was carried out through an observation, videotaping and an interview. Upon examination of these data collection procedures, it was found that problem solving tasks is a useful tool when fostering students’ high order thinking skills. This research highlights the importance of contextualized tasks and argumentation as key components to developing students´ critical thinking skills.