Nurses play a key role in providing care to mechanically ventilated ICU patients and suctioning their secretions. Endotracheal suctioning is a major nursing procedure. Using closed suctioning systems is preferable to open suctioning systems for several reasons. Enhancing the nurses’ motivation for using the closed suctioning system (CSS) can accelerate the patients’ recovery. This study uses motivational interviews to enhance ICU nurses’ internal motivation for change. The present study was conducted to examine the effect of motivational interviews on the level of motivation and self-efficacy for the use of CSS in ICU nurses at Shohada Tajrish Hospital in Tehran in 2015 . the present quasi-experimental pretest posttest intervention study was conducted on a sample population of all the ICU nurses at Shohada Tajrish Hospital in Tehran, selected through census sampling. The subjects were randomly divided into equal groups of cases and control (n=30). Both groups filled out the General Self-Efficacy Scale and the Work Motivation Scale before beginning the study. The intervention consisted of five 90-minute group sessions carried out over three weeks. Three months later, both groups completed the scales once again as the posttest. The analysis of the data was carried out in SPSS-18. Descriptive statistics were then used to describe the data, inferential statistics to test the hypothesis and the Kolmogorov-Smirnov test and the ANVOCA for identifying the relationship between the variables. the mean posttest score of job motivation and self-efficacy increased in the intervention group. The results of the ANCOVA also showed that motivational interviews had a meaningful impact on the examined ICU nurses’ motivation for the use of CSS (P<0.05). Motivational interviews also had a meaningful impact on the nurses’ self-efficacy for the use of CSS (P<0.05). Motivational interviews can therefore be regarded as an effective technique for enhancing motivation and self-efficacy in ICU nurses for the use of CSS.