In the 21st century, education must include the 4C characteristics (critical thinking, communication, collaboration, and creativity) of students. Weaknesses in the learning process and the use of inappropriate models prevent vocational school graduates from mastering these characteristics, which have a significant impact on industrial performance. This research aims to improve students’ critical thinking skills and learning outcomes after implementing problem-based learning. The research methodology used is classroom action research, which is a population study involving all TFLM 3 class students at SMKN 26 as subjects. This classroom action research involves four stages: action planning, action, observation, and reflection. Data was collected through interviews, observation, tests, and documentation. Research data in cycle I did not show an increase in critical thinking skills, with an average of 52.70% (less critical). Therefore, cycle II continued, where there was also no adequate increase in critical thinking skills, with an average of 60.38% (pretty critical). Next, cycle III was carried out, and it reached an average of 75.64% (good critical). Student learning outcomes also increased over three cycles, from 45.71% in the first cycle (low), rising to 65.71% in the second cycle (medium). Statistical analysis using the t-test shows significance. Tcount = 17.598 exceeds ttable = 1.084, which indicates significant changes in critical thinking as well as significant improvements in student learning outcomes using problem-based learning. Based on the research results, it can be concluded that problem-based learning is very effective in improving critical thinking skills and learning outcomes of vocational school students.