Hyperosmolar Hyperglycemic State (HHS) is one of the acute diabetic complications that commonly seen with type 2 diabetes mellitus (T2DM). This represents a critical case necessitating prompt and efficient intervention to prevent potential severe complications. Nursing plays a crucial role in the care of these patients at the critical care settings. Specifically, the project aims to investigate whether nurses' HHS knowledge can be enhanced by educational programs. Quasi-experimental design was used to investigate the effect of the educational program on nurses’ knowledge about HHS at Al-Diwaniyah Teaching Hospital in three unites: Cardiac Care Unites (CCU), respiratory care unit (RCU) and emergency room (ER). A non-probability (purposive) sample was chosen from nurses who works in these three unites, the study group consisted of 35 nurses, while the control group comprised 41 nurses. A statistical package for social science (SPSS) program, version 26 was used for descriptive and inferential statistics. By comparing the nurses’ knowledge about HHS between the test before (6.4286± 1.35659) and after the program (8.2000± 1.10613), there is a significant difference in nurses’ knowledge after the program in the study group, but as for the control group, there is no difference. By comparing the nurses' knowledge regarding nursing care of HHS between the test before (14.0286± 2.05062) and after the program (16.6286± 1.41600), there is a significant increase in nurses' knowledge about nursing care of HHS after the program in the study group. The finding of study show that the educational program was effective to enhance nurses’ knowledge about HHS.