This study sets out to explore the effect of a subjective well-being intervention program on university students' subjective levels of well-being. The study was conducted with 24 university students (18 women and 6 men) aged between 17 and 23 (X= 18.75), studying in a class called Psychological Counseling and Guidance at the Atatürk Faculty of Education, Marmara University, Istanbul. The data-collecting instruments were "Subjective Well-Being Scale" and "NEO Five-Factor Personality Inventory (NEO-FFI)". Students in the experimental group joined a "subjective well-being intervention program" developed by the researcher. Students in the control group did not receive any experimental treatment. The "Mann-Whitney U test" and the "Wilcoxon signed-rank test" were used for data analyses. The findings showed that the subjective well-being intervention program was effective in increasing students' levels of subjective well-being. The follow-up test, carried out three months later, indicated that the effect of the program was permanent.