This quasi-experimental research aimed at investigating the effect of ProblemOriented Project-Based Learning (POPBL), Student Team Achievement Division (STAD), POPBLSTAD integration, and conventional learning on students' critical and creative thinking skills. Essay tests conducted to 129 students. The results of the test assessed using a relevant rubric. Posthoc analyses, namely LSD and effect size analyses, were used to analyze the data. The results of the ANCOVA analysis show that the learning model had a significant effect on students' critical thinking skills as well as on their creative thinking skills. The LSD analysis result showed that POPBLSTAD integration achieved a higher score of critical thinking compared to STAD, POPBL, and conventional learning (21.22%, 16.11%, and 39.38%, respectively). Likewise, related to creative thinking, the POPBLSTAD integration score was 25.91%, 18.57%, and 53.29% higher than those of STAD, POPBL, and conventional learning, respectively. Besides, all effect size analyses showed that POPBLSTAD obtained a higher effect-size score in critical thinking (high criteria) compared to STAD, POPBL, and conventional learning (0.68, 0.65, and 0.82, respectively). Similarly, the POPBLSTAD integration achieved a higher effect-size score of creative thinking (high criteria) compared to STAD, POPBL, and conventional learning (0.66, 0.55, and 0.83, respectively). Both analyses have demonstrated similar interpretations; thus, the two types of analyses should simultaneously be used to obtain complete research information.