To assess the impact of educational intervention by nurses guided by Orem's theory to reinforce the self-care abilities of patients experiencing myocardial infarction. The prospective, quasi-experimental case-control study was conducted from September 2020 to April 2021 at Dr. Ruth K.M. Pfau Civil Hospital, Karachi, and comprised myocardial infarction and heart failure patients with comorbidities diabetes mellitus and hypertension. The patients were randomised into experiment group A and control group B. Group A received educational intervention one day before and one day after discharge in line with the American Heart Association guidelines. Two 30-45-minute sessions of seven modules were conducted. Group B received routine information from ward staff. Assessment was done at baseline and first month and second month post-intervention using the Heart Failure Self-Care Index version 6.2. Data was analysed using SPSS 21. Of the 80 patients, 40(50%) were in group A; 27(76.5%) males and 13(32.5%) females. The remaining 40(50%) patients were in group B; 20(50%) males and 20(50%) females. The overall age of the sample ranged 36-65 years and 48(60%) had a previous history of heart failure. The mean score of maintenance, management, confidence and overall self-care were significantly higher in group A compared to group B (p<0.05). Nursing self-care educational intervention based on Orem's theory was found to be highly effective among patients of myocardial infarction and heart failure with respect to their self-efficacy ability.