The purpose of this study is to evaluate the effect of preventive nursing measures on the delirium incidence of the patients with open heart surgery. This is a semi-experimental interventional study which will be carried out in 2015. Research sample includes 72 admitted patients at open heart surgery unit of Sari Fatima-Zahra Hospital. These patients have to be over 18 years with no delirium before surgery and its preoperative history and are subject to an elective open heart surgery. Exclusion criteria in this study are Impairment of consciousness, using psychological drugs, having a depressive disorder, recent use of opiate drug and alcohol, absolute blindness and deafness, emergency heart surgery, died during surgery or during investigation and Patients refuse to cooperate with preventive nursing measure during the study. All patients in the study are sampled based on availability and divided into two groups of control and intervention. At first, Researcher starts sampling without intervention from control group. After sampling from this group, Intervention will be initiated through preventive nursing measures and environmental changes. These interventions will be continued from the first day after surgery till the end of fifth day. Patients in both groups are evaluated in terms of delirium incidence based on NEECHAM every afternoon. Patient information questionnaire have to be completed by researcher one day before surgery. Delirium incidence cases can be recorded using a check list. A comparative study of delirium incidence in the two study groups are carried out.