The purpose of the present study was to increase the self-formation consciousness of female high school students, using an intervention based on individuals’ character strengths.  The participants, high school girls (average age 16.6 years), first completed an inventory of their character strengths; in the next week, they received individualized feedback about their top 5 scores on the character strength inventory, and the intervention group was asked to use one of those strengths in a new and different way each day for 1 week.  All participants completed a self-formation consciousness scale before and after the intervention.  In the feedback and post-intervention periods, participants in the intervention group also completed an intervention that assessed their feelings about their top 5 strengths.  Changes in the 2 groups during the intervention were analyzed using a 2×2 (Condition × Time) mixed ANOVA.  The results suggested that the possibility-seeking scores and the effort-to-possibility scores of the students in the intervention group increased significantly from the time of the pre-test to the time of the post-test.  In addition, a significant increase from the feedback test to the post-test was found in the intervention group’s scores on their feelings about their character strengths.  These findings suggest that the intervention using the students’ top 5 character strengths appeared to be effective in self-formation consciousness.