This study was carried out to determine the effects of positive psychology intervention on self-efficacy and psychological hardiness of female students. The statistical population of the study comprised all female students attending public high schools in District 4 of Tehran in school year 2017-18. The drawn sample was selected through multi-stage cluster sampling method and the subjects were randomly assigned to experimental and control groups (15 in each group). Positive psychology training was provided to the experimental group during eight 120-minute sessions and the control group received no intervention.Self-efficacy and psychological hardiness of the participants were assessed by General Self-Efficacy Scale (Sherer et al., 1982) and Psychological Hardiness Scale (Kobasa & Kahn, 1982) before and after the intervention. The obtained data were analyzed through analysis of covariance (ANCOVA). The results indicated that positive psychology intervention improved the self-efficacy and psychological hardiness (commitment, control, and challenge) of the intervention group compared with the control group. In general, it can be stated that positive psychology interventions can improve self-efficacy and develop psychological hardiness. Consequently, positive psychology training can be used to reduce students’ psychological problems.