This was a quasi-experimental study with a pretest-posttest design, a control group and follow-up. The study population included all high school students in the city of Torbat-e Jam (Iran) in 2016. The subjects were selected via availability sampling and then randomly assigned into two groups of 20 (an experimental and a control group). The subjects in the experimental group participated in 60-minute weekly self-efficacy group training sessions for seven weeks. No intervention was done for the control subjects. After the training sessions, the achievement motivation and self-efficacy scales were used to collect posttest data. The collected data were analyzed with SPSS (version 16) using descriptive statistics, analysis of covariance, the Levene’s test, regression analysis and the Bonferroni post-hoc test. All statistical analyses were performed at significance of 0.05. Results: After the training period, the mean self-efficacy score increased from 13.76 ± 3.02 to 14.34 ± 3.47 and the achievement motivation score increased from 12.58 ± 6 to 14.37 ± 4.1. There were statistically significant differences in terms of pretest and posttest scores between the two groups. Results after two months of follow-up also indicated that the intervention results persisted in the experimental group. Conclusions: Considering the positive impact of the self-efficacy group training on self-efficacy and achievement motivation, it can be suggested as an effective cognitive intervention in educational counseling.