This study investigated the impact of thinking instruction on students' metacognition and thinking behavior. Higher-order thinking occurs when individuals use their underlying metacognitive strategies which increase the probability of achieving a desirable result. The study was designed as a case study of an intervention and a posttest-only control group design was adopted. Participants consisted of students with a variety of majors were recruited from a medium-size university located in southern Taiwan. Two classes of the Developing Thinking course, totaling 78 students, comprised the group receiving the intervention, while 196 students in six General English classes comprised the comparison group. The intervention students were introduced to thinking skills, facts and opinions, question stems, and thinking from different perspectives. The quantitative results show strong evidence that the thinking instruction exerts statistically significant positive effects on students' metacognition. Qualitative evidence also shows improvements in cognitive awareness with students demonstrating a more consistent application of thinking skills, an increased ability to think critically with thinking dispositions cultivated, and most importantly, a transfer of thinking behavior across the curriculum and in their personal lives. The researcher suggests the value of introducing thinking instruction to promote critical thinkers.