Purpose: This descriptive correlation study was done to investigate the influence of older person s ego integrity and knowledge of advance directives on their attitude toward withdrawal from life-sustaining treatment. Methods: The participants were 155 older persons residing in B city. Data were collected from February 11 to March 8, 2019. Data analysis was performed using descriptive statistics, t-test, one-way ANOVA, Pearson correlation coefficient, and stepwise multiple regression analysis. Results: Ego integrity was positively correlated with knowledge of advance directives and attitude toward withdrawal from life-sustaining treatment. Knowledge of advance directives was positively correlated with attitude toward withdrawal from life-sustaining treatment. The factors influencing attitude toward withdrawal from life-sustaining treatment were participants economic status, ego-integrity and knowledge of advance directives. These variables explained 17.1% of older person s attitude toward withdrawal from life-sustaining treatment. Conclusion: The findings indicate that ego integrity and knowledge of advance directives are important factors in changing older people s attitude toward withdrawal from life-sustaining treatment. Therefore, systematic programs to enhance the older person s ego integrity level and improve their knowledge of advance directives should be developed.