Background: Critical thinking is an important student learning outcome in all psychology courses and included in the American Psychological Association's (APA's) goals for the undergraduate major. Objective: The purpose of this study was to test the effectiveness of integrating a general model of critical thinking into the instruction, assignments, and discussions in an online course on students' development of critical analysis and evaluation skills. Method: Two raters scored 34 students' written responses on a critical thinking test administered at the beginning and end of the semester that had students analyze psychological studies as reported in media reports and evaluate position statements on a controversial issue. During the term, students completed assignments on identifying the parts of a scientific study and discussions on identifying weaknesses in thinking. Results: Students showed large gains in critical analysis and critical evaluation scores from pretest to posttest. Specific comparisons revealed that students significantly improved their abilities to identify the theoretical point of view of a study, relevant psychological concepts, assumptions, and implications. Conclusion: Integrating critical thinking in a direct way into a course can lead to substantial improvements in critical thinking over the span of a single semester.