To enhance students' critical thinking in an undergraduate general science course, we designed and implemented active learning modules by incorporating group-based learning with authentic tasks, scaffolding, and individual reports. This study examined the levels of critical thinking students exhibited in individual reports and the students' critical thinking level change over time. Findings indicated that students' average critical thinking level fell in the category of "developing", but students' scores on individual reports revealed a statistically significant increase. The study suggested that the active learning strategies employed in the study were useful to promote student critical thinking.