Speaking is considered to be the most complex skill to master by EFL (English as a foreign language) learners. Unfortunately, Ecuadorian students do not reach the desired speaking level. To address this issue, this mixed-method study aims at identifying the impact of critical thinking activities through workshops, in order to improve learners’ speaking skills.  This study was conducted at public high schools in the different provinces of Ecuador. The sample consisted of 635 students from the tenth grade of elementary school and the first and second grades of senior high school. The data-collection instruments were a pre-test, and a post-test, to find out the students´ CEFR speaking level, and an observation grid to discover students’ attitude and performance concerning oral communication skills. Additionally, five different workshops, based on the use of critical thinking activities were carried out. The results led us to the conclusion that critical thinking workshops have a positive impact on students’ speaking skills. They allowed students to use accurate grammar, vocabulary, and to improve their fluency and pronunciation, in order to communicate their ideas orally.