With the correct approach to education, students may develop their capacity for critical thinking. With the use of the phypox app, this research intends to detail how well a problem-based learning paradigm may improve students' critical thinking abilities. Eleven students from Science 2, 4, and 5 at SMA Negeri 22 in Surabaya participated in this quasi-experimental study by taking pre- and post-tests as a group. A quantitative descriptive approach was used for data analysis. With an average n-gain score of 0.80 for XI Science 2, 0.83 for XI Science 4, and 0.78 for XI Science 5, the findings demonstrated that students' critical thinking abilities increased. Classes 4 and 5 of the XI Science program had the greatest and lowest n-gains, respectively. And a Non-Parametric Anova Test result of 0.13 was achieved. After considering the evidence, it is clear that phypox-assisted problem-based learning significantly enhances high school students' critical thinking abilities.