This study aimed to present and test a model of the effect of the students' locus of control on happiness with the mediation role of optimism and hope. Therefore, 377 participants, including 234 males and 143 females, were selected from among the students of a nonprofit institute of higher education and then were asked to respond to Rotter's Locus of Control and Adult Hope Scales, Oxford Happiness Questionnaire, and Life Orientation Test. Structural equation modeling was used to test the research model. Also, to investigate the indirect effects of the research model, the bootstrapping method was used. The results showed that the fit indices for the research model were in the favorable range; therefore, the model was consistent with the data. Also, the model's direct effects showed that locus of control affected the optimism was significant. The effect of hope on happiness was significant; the locus of control and optimism on hopefulness was also significant. Still, the effect of optimism on happiness was not significant. Finally, the results showed that all of the indirect effects were significant. The locus of control has a significant impact on the mediation of optimism and hope, on the students' sense of happiness. Therefore, it seems necessary to consider these factors as influential factors promoting happiness.