Character strengths represent positive durable attributes of individuals and their deployment is hypothesized to positively affect mood and well-being. Furthermore strengths deployment may serve as a mood-repair strategy which promotes growth. Close relationships being potential facilitators of personal growth were hypothesized to amplify these two effects. These hypotheses were examined in a quasi-experimental diary study. Participants (N = 150) completed daily measures of strenths deployment and mood. They were randomly assigned to a relationship-exercise condition (writing a daily note to a loved one) or to one of two control conditions. Previous-day strengths deployment was associated with more positive daily mood and previous-day adverse mood predicted increased strengths deployment. The first effect seemed to be somewhat stronger in the relationship-exercise condition. These results highlight positive daily effect of strengths deployment demonstrate the use of strengths to combat adverse mood and suggest that close relationships enhance the positive effects of strengths deployment.