Anger and related problems are common conditions in everyday life. Anger is often experienced as a feeling that leads to disruptive consequences. Often, anger can be seen among young people, especially in romantic relationships. This case study didactically presents rational-emotive behavior therapy treatment of dysfunctional anger in an 18-year-old Turkish woman. The client mostly experienced intensive anger problems including physical signs and symptoms. The therapy sessions covered the client’s problems with her boyfriend. Treatment focused on disputing irrational beliefs, engaging in imaginal exposure, providing psychoeducation about the principles of rational-emotive behavior therapy, and cognitive restructuring. Treatment was provided in eight sessions with a three-week follow-up. The client filled out the Oxford Happiness Questionnaire – Short Form and the Trait Anger and Anger Expression Scale. The questionnaires were used during the pre-test, mid-test, post-test, and follow-up. The psychometric scores were clinically significant. Levels of happiness and anger control increased, moreover the level of anger decreased after the end of the rational-emotive behavior therapy-based sessions.