This study aimed to investigate the effect of online, flipped, and in-class critical thinking teaching on critical thinking skills and dispositions of university students. Pretest-posttest control group quasi-experimental design was employed in this study that has three experimental groups and one control group. In the first experimental group, critical thinking teaching was conducted fully online. In the second experimental group, flipped classroom approach was employed while teaching critical thinking. In the third experimental group, critical thinking teaching was conducted in face-to-face classes. Watson-Glaser Critical Thinking Test and Sosu Critical Thinking Dispositions Scale were used to collect the data. Online, flipped, and in-class explicit critical thinking instructions enhanced university students' critical thinking skills and dispositions with a large effect. Also, the most effective learning environment to promote critical thinking skills and dispositions was flipped, online, and in-class, respectively.