The purpose of this study was to test the effects of a self-help nursing intervention on adolescent psychosocial competence. A community sample of 139 adolescents was assigned to three conditions (intervention, delayed intervention, and control) within a pretest-posttest design. The self-help nursing intervention was a 9-page, 14-step self-help workbook for use by adolescents in dealing with upsetting situations in day-to-day living. After a self-assessment of coping, subsequent workbook steps aided adolescents in developing alternate coping responses and generating other ways to deal with the upsetting situation. Adolescents in the three conditions did not differ on pretest measures of psychosocial competence: problem-solving appraisal, adolescent self-perception, and general self-efficacy. After statistically controlling for pretest scores, gender, and age, the intervention group showed more favorable self-perceptions in scholastic competence, social acceptance, and conduct/morality compared with the control group. However, expected differences in the delayed intervention group failed to appear. Thus, anticipated benefits in psychosocial competence were found inconsistently. Although not predicted, significant reductions in the prevalence of negative affect occurred among adolescents in both intervention groups. Overall, the self-help format for delivering psychosocial competence training lacked the power needed to bring about consistent benefits for adolescents. Testing the self-help workbook in a group context is recommended in future nursing intervention research.