The needs of our society are quickly evolving and soft or transferable skills are key to lifelong learning and the creation of an adaptable and resilient workforce. There is an ever-growing demand for individuals who can process data, evaluate concepts, and develop arguments; the development of critical thinking skills is crucial. This study shows the effectiveness of a professional development model that aimed at improving teachers’ instructional design skills for nurturing critical thinking in the classroom. The study adopted a quantitative research approach in order to identify and assess the transformation in teachers’ pedagogical practices while developing lesson plans designed to elicit and nurture critical thinking among their learners. This study focused on a sample of 16 teachers at a secondary school in Central Uganda. The researcher purposefully selected the teachers, who specialised in three different subjects: English (5), mathematics (5), and history (6). The teachers who participated in the study were on average 32 years old and had 8 years of teaching experience. To evaluate the effectiveness of the lesson plans that the participants designed, the researcher developed a contextualised rubric that was then validated by experts to assess the teachers’ improvements in designing lessons for critical thinking enhancement. The findings confirmed that after the training intervention, the teachers showed a greater ability to differentiate between cognitive process and mere rote learning, helping them to elicit critical thinking in their students. At the end of the process, the lesson plans designed were clearer and more coherent, incorporating activities that could improve the learners’ critical-thinking skills. This study provides an important contribution in terms of how to promote contextually appropriate and innovative pedagogical strategies.