Sleep is one of the major requirements for patient’s recovery. Given the role played by environmental factors in patient’s sleep disorders in a Coronary Care Unit (CCU), it is necessary to use an appropriate protocol to improve these patient’s sleep. The present study investigated the effect of Quiet Time protocol (QT) on the sleep quality of cardiac patients in the city of Ilam. The present clinical trial was performed in 2015, using cardiac patients in Ilam. The patients were divided into two groups: (1) Experimental and (2) Control groups. Data were collected using a demographic questionnaire, St. Mary's Hospital Sleep Questionnaire (SMHSQ) and Epworth Sleepiness Scale (ESS). The quiet time protocol was carried out with the experimental group from 11 pm to 5 am for three consecutive nights. Data analysis was performed using descriptive statistics (mean and standard deviation), Fisher’s exact test (to compare the two groups in terms of number of days of hospitalization in the CCU before treatment) and independent t-test (to compare the patient’s age difference and sleep hours at home). The findings showed that sleep quality was low in patients before Quiet Time protocol (QT). There was no significant difference (p>0.05) between sleep quality of the QT group and the control group on the first night. Given that the quiet sleep protocol improves the quality of patient’s sleep, the implementation of this protocol is recommended to patients receiving nursing care.