This study aimed to examine the effect of motivational interviewing on healthy lifestyle behaviors and biochemical parameters in patients who underwent stent implantation after coronary angiography. Specifically, it investigated whether a structured motivational interviewing program could improve patients' health-promoting behaviors and positively influence biochemical outcomes such as blood lipid levels and body mass index (BMI). The research was designed as a randomized controlled study and was conducted in the cardiology outpatient clinic of a training and research hospital in Istanbul. The study included patients diagnosed with coronary artery disease who had undergone coronary angiography followed by stent implantation and were being followed in the outpatient clinic. Participants were randomly assigned to either the intervention group or the control group. In the intervention group, patients received a motivational interviewing-based program over a three-month period. This program included face-to-face educational sessions lasting approximately 30-45 minutes, focusing on coronary artery disease, risk factors, healthy nutrition, physical activity, stress management, sleep regulation, and smoking cessation. In addition, participants received reminder messages twice a week to support behavioral change and encourage adherence to healthy lifestyle practices. The control group continued their routine medical follow-up and standard care without additional intervention. Data were collected at baseline and at the end of the third month. In the intervention group, data were additionally collected at the end of the first month. Both groups were evaluated using the Health-Promoting Lifestyle Profile II scale, and biochemical parameters including HDL, LDL, total cholesterol, triglycerides, and BMI were measured and recorded. The study aimed to determine whether motivational interviewing could serve as an effective nursing intervention to promote sustainable lifestyle changes and improve clinical outcomes in patients with coronary artery disease following stent implantation.