Purpose: The purpose of this study was to investigate the effects of self efficacy, and health related hardiness on a health promoting lifestyle of middle-aged people Method: The study was designed as a descriptive survey study. Data was collected using a structured questionnaire which included general characteristics, measure of self efficacy, health related hardiness, and health promoting lifestyle. Data collection was done between May and August, 2007 with 197 middle-aged participants. Result: The average score of the participants for self efficacy was 34.78, for health related hardiness 57.01 and for a health promoting lifestyle 127.53. There were positive correlations between self efficacy and a health promoting lifestyle, health related hardiness and a health promoting lifestyle, and self efficacy and health related hardiness. The correlations were statistically significant. Health related hardiness was a significant predictors of a health promoting lifestyle. Conclusion: A strategy for improving self efficacy and health related hardiness should be developed and a nursing intervention program should also be provided based on the developed strategy of middle-aged people.