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Aim and Background: Many studies have shown that mortality rate among the patients with coronary artery diseases (CAD) is greatly influenced by their mood. While positive psychological states are associated with improved cardiovascular function in these patients, positive psychology interventions have not been used in patients with cardiac diseases. Hence, this study examined the effectiveness of three happiness interventions on psychological variables in patients with cardiac diseases. Methods and Materials: In present study, 68 patients with cardiac diseases were assigned randomly to three happiness intervention groups, including Seligman, Lyubomirsky and Fordyce, and a control group. The intervention groups completed 6 weeks of happiness sessions, and pre-intervention, post-intervention and follow-up measurements were carried out on the patients. Assessments included the status of depression, happiness, life satisfaction and hope. Data were analyzed with one-way repeated measures analysis of covariance. Findings: All three interventions improved happiness in patients significantly (P < 0.01). In addition, significant reduction of depression in Fordyce group was observed (P < 0.05). Besides, hope increased significantly in Seligman group at posttest and follow-up (P < 0.05). Conclusions: These findings show that these happiness interventions may be led to more promising results in promoting positive psychological states and reducing depression in patients with cardiac diseases. In general, Seligman happiness intervention in promoting positive psychological states and Fordyce happiness intervention in reducing depression lead to better outcomes than two other interventions.