Introduction: This study identifies and analyzes the levels of relations between decision-making competency, self-determination, and health lifestyle in nursing students. Methods: This study was designed as a descriptive research to identify the relations of nursing students’ decision-making competency, self-determination, and health lifestyle. The subjects were 187 nursing students. Data were collected using a structured questionnaire and were analyzed by the IBM SPSS Statistics 19 program. Results: Decision-making competency of nursing students was 3.38 ± 0.41 points, and self-determination was 3.07 ± 0.38 points. Stress and physical exercise were the general and health-related lifestyle factors that contributed to the differences in decision-making competency. There were no differences in self-determination according to these factors. Conclusion: The results of the study showed that the levels of decision-making competency and self-determination in nursing students were moderate. Further studies are recommended for the development of these core abilities in nursing students.