Objectives: Secondary prevention of ischaemic heart disease (IHD) is very important. This study aimed to assess knowledge of necessary lifestyle changes among Omani patients diagnosed with IHD. Methods: This cross-sectional pilot study took place between October 2015 and February 2016 at the Sultan Qaboos University Hospital (SQUH), Muscat, Oman. A total of 30 random patients with IHD from the Cardiology Outpatient Clinic of SQUH were included. A 30-item survey was used to determine patients’ knowledge of necessary lifestyle practices following their IHD diagnosis, with scores of 70% indicating poor knowledge. Results: Overall, 21 patients (70.0%) had low knowledge levels. Scores ranged from 38.9−94.4% (mean: 60.7% ± 14.1%). No demographic factors were found to predict low scores, although there were some differences in individual questions. Conclusion: Low knowledge levels regarding lifestyle changes were observed among IHD patients in Oman. More efforts should be made to educate these patients for the secondary prevention of IHD.