The aim of the research was to know the effect of implementation of problem-based learning model on students' physics achievement and critical thinking. The research was a quasi-experimental using a pre-test-post-test control group design. It was conducted at a state senior high school in Indonesia. The data were collected by a students' physics achievement test, a students' critical thinking test, and an observation sheet. The data were analysed by calculating normalized gain scores and hypothesis testing by using MANOVA with the significance level of 0.05 as criterion. The research results indicated that the average gain scores for students' physics achievement of the experimental and control groups were respectively 0.63 and 0.32, the average gain scores for students' critical thinking of the experimental and control groups were respectively 0.49 and 0.34, and a value of p is 0.0001 was obtained from the MANOVA calculation so that it is concluded that such learning as that in the experimental group is better in comparison with such learning as that in the control group. The results of this research are expected to increase insight and knowledge of teachers in implementing the learning process in the classroom so as to apply varied learning models.