The purpose of this study is to determine the relationship between adherence to cardiac rehabilitation (CR) and improvements in health-related quality of life (HRQL) with a 12-week, Phase-II CR program. Previously collected data from 153 CR patients (114 males, 39 females; 69.1 years of age ± 11.5) were utilized to complete this retrospective study. Patients completed the Medical Outcomes Survey Short Form-36 to assess HRQL at the beginning of CR (N = 153), at 3 months (N = 152), and at 1 year (N = 94). Pearson correlation coefficients were generated to assess the relationship between CR attendance and HRQL. Paired sample t-tests helped determine the effect of CR on HRQL at 3 months and 1 year. No relationship was found between CR adherence and improvements in HRQL. Significant improvements in HRQL were found among all patients from baseline to 3 months and 1 year. Study findings demonstrate the effectiveness of CR in improving patient short- and long-term HRQL regardless of patient adherence rate.