Background & aim: Delirium is a prevalent disorder that frequently appears in inpatients and is followed by undesirable consequences and complications. Considering the role of nurses in determining and preventing delirium, investigating nurses’,understanding of the care of patients with delirium is crucial. The present study was conducted in order to explain the experiences of nurses caring for patients with delirium. Methods: The research population consisted of nurses who work in Shahid Beheshti hospital. Eleven nurses were selected by purposive sampling method. The selection criteria of participants included consent to participate in the study, having at least a Bachelor’, s degree, and working experience of more than 5 years. For data collection, a semi-structured focus group discussion method was used. The time, place, and duration of the sessions were coordinated based on the participants’,preferences. Every Focus Group Discussion session lasted about 60 minutes. Data were analyzed by conventional content analysis method with an inductive approach. Results: The result of the study showed that nurses differently understood delirium, considering their experiences and based on this, they stated variable factors in its occurrence. According to this study, individual factors, family neglect, ineffective communication, fear of the unknown and unstable environment were identified as the roots of delirium. The three main categories of the findings of the present study were ‘, lost in time and space’, , ‘, unbridled behaviors’, , and ‘, the underlying cause of delirium’, . Conclusion: As reported by nurses, delirium is characterized by some features including loss of time and space and unbridled behaviors. Also, they listed other factors such as individual underlying factors, fear of the uncertainty, ineffective communication, and unstable environment as effective roots in the occurrence of delirium. Based on the results of the present study and considering the role of nurses in the prevention and control of delirium, compiling delirium prevention guidelines and programs in accordance with international guidelines is recommended to be used by nurses.