This action research reports a study carried out in a private high school located in the southeast of Mexico. The aim was to improve students' performance in a B2 language test by acknowledging additive-adversative cohesive devices (whereas, while, however, on the other hand). To this end, an action plan was implemented in a group of 16 students who were enrolled on a B2 language course. To evaluate the action plan, pre- and post-speaking tests were administered, and also, semi-structured interviews were carried out. The results of the post-test showed that most of the participants improved in terms of fluency and coherence. Moreover, during the interviews some students agreed that the targeted cohesive devices were helpful in the organisation of their spoken discourse. Findings of the study contribute to present literature on teaching cohesive devices or discourse markers explicitly in foreign language classrooms.