This study aimed to determine the effectiveness of critical thinking aspects on the module to enhance students' academic achievement of human circulatory system. Research participants were 8th grade of junior high school students, which assigned into experimental and control groups (each group consists of 27 students) based on One-Way ANOVA result (0.255; p-value > 0.05). This quasi-experimental study applied a pre-test and post-test non-equivalent control group design. An analysis of covariance (ANCOVA) was used to analyse pre-test and post-test data, with pre-test as a covariate. Analysis result showed that: (1) students' academic achievement in the experimental group is significantly different with the control group (F=90.562; p-value < 0.05); (2) students' academic achievement gap in the experimental group is lower than the control group; and (3) applying critical thinking aspects on the module have an effective contribution of 64% in students' academic achievement enhancement of the experimental group. Therefore, the use of critical thinking aspects on the module has a good impact on students' academic achievement.