Background: The critical care unit is one of the important units in the hospital that receives critical and dangerous cases. There are medications used in these units, including shock medications. The nurse must have enough knowledge about these medications to reduce the rate of medication error and prevent harm that occurs to patients. Aims: to determine nurses' knowledge of drugs used in critical care units and to find the relationship between nurses' knowledge and their demographic data. Methods: A quantitative descriptive study was carried out in Critical Care Units affiliated with Al-Furat Al-Awsat Hospital, Al-Hakim General Hospital, and Al-Saddr Teaching Hospital in Al-Najaf City/Al-Najaf Al-Ashraf Health Directorate. A non-probability (convenience) sample of 77 nurses was obtained from the above settings, regardless of their characteristics. The study began from December 10th, 2022 to April 1st, 2023. Data were collected through a special questionnaire prepared to collect the data which was divided into two parts. The validity of the questionnaire was acquired by examination of (13) experts in different fields, and correlation was utilized as a statistical approach to evaluate the reliability of the study questionnaire. Data were analyzed using descriptive and inferential statistics. Results: The general assessment of the nurses' knowledge regarding drug in intensive care units was fail with an average score of less than (1.50), as the scores were unsatisfactory concerning medication administration. Conclusion: A study concluded that a nurse's knowledge about the medications used in intensive care units was Low, less than (1.50) overall.