This action research aims at exploring the contribution of self-assessment checklists on improving oral presentations of two participants that were taking an initial-level English as a second language course at a technician professional institute in Talcahuano, Chile. The intervention was carried out in four weekly sessions in which the participants were trained on the different criteria to assess their oral presentations. The participants self-assessed their work with a checklist and performed a second presentation based on their first self-assessment. Analytic rubrics were also used as an external assessment to compare results from the checklists. At the end of the intervention, a semi-structured interview was conducted to obtain the participants' perceptions about the process. Findings reveal that by developing autonomy, language awareness, and self-reflective skills, the use of the self-assessment checklist supported the participants not only to improve their oral presentation in overall aspects, mainly in fluency and pronunciation aspects, but also to make positive changes in their confidence and expectations about their performance.