Self-efficacy (SE) is an important outcome following cardiac rehabilitation (CR) when claiming benefits to patients and improving existing programs. This study evaluated change in SE during 6 weeks of multidisciplinary CR with either a high or low-frequency exercise training program. The role of overprotectiveness of the spouse, as it potentially counteracts improvement in SE, was examined. Coronary patients (n = 114) were randomized into both types of program. Overprotectiveness (patient perception) was assessed prior to rehabilitation. Self-efficacy in the domains controlling symptoms (SE-CS) and maintaining function (SE-MF), were assessed prior to and immediately after rehabilitation. Three findings pertain to program improvement: (1) As predicted, the low-frequency program enhanced SE-CS more than the high-frequency program, suggesting that experiencing success in daily activities and active engagement of the patient seem more decisive factors in improving SE than the frequency of exercise. (2) Changes in SE in both programs fell short of clinical meaning, suggesting the need to use self-efficacy theory more vigorously. (3) Overprotectiveness significantly predicted adverse change in SE in the high-frequency program, suggesting the need to include counseling for cardiac couples in CR when applicable.