Delirium is a common complication in hospitalised patients, however it is often misdiagnosed by health care professionals. Failure to achieve a timely diagnosis results in poor outcomes, prolongation of patient hospitalization, increased costs of hospitalization, increased morbidity and mortality. Aim: To investigate the level of knowledge of nurses with regard to delirium and the care of hospitalized patients with delirium. Material - Method: A cross-sectional questionnaire survey was carried out with a sample of 108 (N=108) nurses working in medical and surgical wards in two general hospitals of Athens and in three provincial hospitals. For the data collection, a 28 item questionnaire was developed, based on a preexisting research tool as well as on the relevant literature. The questionnaire additionally demonstrated high reliability (Cronbach's a=0,860) as well as face and content validity. Respondents also answered open questions on knowledge regarding the nursing care of patients with delirium. Descriptive and inferential statistics was used for the data analysis. Content analysis was used in analyzing data gathered from the use of open questions and results were presented in percentages. Results: The majority of nurses answered incorrectly or declared that they did not know, in 17 of the 28 questions in relation to delirium. Of the respondents 63,8% were unable to answer with clarity in open questions on the care of patients with delirium. 82,4% reported that caring for patients with delirium was based solely on the instructions of doctors. 44,4% answered that patients' care include the administration of anxiolytics, tranquilisers, and the stay of a familiar person next to the patient as well as 80,5% answered the use of patients' restraint. 67,5% of respondents pointed out that they had not been taught in their undergraduate studies regarding delirium. Multiple regression analysis revealed that specialization in nursing and postgraduate studies affect positively at statistically significant level (p<0.05) nurses' knowledge about delirium. Conclusions: Is necessary to incorporate delirium in nurses' curriculum at the undergraduate level. In addition, continuing education courses have to be held in order to provide knowledge on nurses working in hospital settings to help the early detection of the symptoms of delirium and provide effective nursing care.