This study aimed to examine the effectiveness of a career psychoeducation program developed based on the social cognitive career theory in career decision self-efficacy and educational outcome expectations of eleventh grade students. The study used a quasi-experimental model with a pretest-posttest control group design. The experimental process of the study was designed according to a 2x3 mixed (split-plot) design with a control group including pretest, posttest, and follow-up measurements. This process was carried out with 36 eleventh grade students, including 18 in experimental and 18 in control groups. The study data were collected using the Career Decision Self-Efficacy Scale--Short Form and the Educational Outcome Expectations Scale. During the experimental process, an eleven-week career psychoeducation program was carried out in the experimental group, and no intervention was conducted in the control group. As a result of the study, it was found that there was a significant difference in favor of the experimental group students in terms of the mean scores obtained from the career decision self-efficacy and educational outcome expectations and that this difference between the mean scores was also maintained in the follow-up measurements. The findings of the effectiveness of the career psychoeducation program on the career decision self-efficacy and educational outcome expectations of eleventh grade students were discussed in the light of the related literature.