Most schools in the United States report annual teacher shortages. Without teacher instruction, the stability of education and students' future is in jeopardy. Low self-efficacy is one possible cause of the teacher shortage. Preservice teachers report low self-efficacy during field experience in teacher preparation programs. This quantitative quasi-experimental study investigated the effect of critical thinking instruction on preservice teachers' self-efficacy. The study was conducted at a Southeastern United States university with consenting adults enrolled in the next-to-last semester of a teacher preparation program. Bandura's self-efficacy theory provided a theoretical framework, specifically the constructs of vicarious and mastery experiences. A sample of 43 preservice teachers completed the Teachers' Sense of Efficacy Scale-Long Form assessment instrument. One-way ANOVA data analysis showed a statistically significant difference between treatment and nontreatment groups' posttest, F(1, 41) = 7.52, p = 0.009. Two of the three subfactors of the instrument were statistically significant: classroom management, F(1, 41) = 7.30, p = 0.01, and instructional strategies, F(1, 41) = 7.74, p = 0.008. The results indicate teacher preparation coursework focused on critical thinking instruction, classroom management, and instructional strategies may improve preservice teachers' self-efficacy. The study's implications include establishing a policy to monitor critical thinking in teacher preparation programs, adding to literature to support the connection between critical thinking and self-efficacy, and including more training in critical thinking and self-efficacy in professional practice. Future research may replicate the study at other universities to determine the effect of critical thinking skills instruction on preservice teachers' self-efficacy. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]