This study explores how organizational citizenship behavior (OCB) affects teacher happiness at work (HAW) among Islamic-based junior high school teachers. Happier teachers are more effective educators, as workplace happiness enhances their ability to create a conducive learning environment. Schools that foster positive work environments boost teachers' organizational citizenship behavior. The results indicated that OCB dimensions significantly affected HAW, with conscientiousness having the strongest effect. A quantitative approach was employed, using a sample of 131 Islamic-based junior high school teachers. Instruments measuring HAW and OCB were adapted from existing research and analyzed using confirmatory factor analysis (CFA) and Partial Least Squares (PLS). A quantitative cross-sectional survey was conducted using CFA and PLS to analyze multidimensional relationships. The path coefficient was 0.195 (p-value = 0.000), indicating that altruism significantly affects HAW. The path coefficient was 0.184 (p-value = 0.000), indicating that civic virtue significantly affects HAW. The path coefficient was 0.282 (p-value = 0.000), indicating conscientiousness significantly affects HAW. The path coefficient was 0.187 (p-value = 0.000), indicating that courtesy significantly affects HAW. The path coefficient was 0.217 (p-value = 0.000), indicating that sportsmanship significantly affects HAW. The R-Squared was 0.828, which means the contribution of OCB to HAW was 82.8%, which means H6 is accepted. These findings have important implications for both theory and practice, as they highlight the role of OCB in enhancing teacher happiness, particularly in Islamic-based school settings.