Background: Heart attacks among adults are considered one of the most prevalent global health concerns. Aim: to assess the lifestyle of newly diagnosed adults with heart attacks. Design: A descriptive research design was utilized in this study. Setting: The study was conducted in the outpatient cardiology clinics of the Academy of Heart at Ain Shams University Hospital in Cairo governorate. Sample: A Purposive sample of 251 newly diagnosed adults.  Study tool: Two tools were used for data collection: The first tool was a structured interview questionnaire, which consisted of five parts: Part 1: Socio-demographic characteristics of a newly diagnosed adult with heart attacks. Part 2: Knowledge of newly diagnosed adults with heart attacks. Part 3: Reported practices of newly diagnosed adults with heart attacks related to lifestyle. Part 4: Health needs and problems of newly diagnosed adults with heart attacks. Part 5: Lifestyle questionnaire sheet. The second tool: Medical records. Results: The mean age of the newly diagnosed adults with heart attacks was 37.65±5.22. 57.2% of the studied sample had a satisfactory level of total knowledge. 55.6 % of the studied sample reported unhealthy practices. 62.8% of the studied newly diagnosed adults with heart attacks had not achieved health needs. However, 58.4% of the studied newly diagnosed adults with heart attacks had unhealthy lifestyles. Conclusion: More than half of the studied newly diagnosed adults with heart attacks had a satisfactory level of total knowledge. More than half of the studied newly diagnosed adults with heart attacks had unhealthy reported practices. There was a highly statistically significant relationship between total knowledge and total practices, and there was a highly statistically significant relationship between total problems and total practices. Recommendation: A health education program to increase the adult's knowledge, improve their practices, and teach them the importance of early treatment and healthy lifestyle guidelines.