Abstract : Background: Although poor sleep quality may decrease nurses' performance, the association between the two has not yet been evaluated in Bahrain. Sufficient sleep quality empowers a well-balanced immunity, supports work performance, and work safety. This need is particularly important in the population of nurses who encounter a different shift pattern. The risks associated with poor sleep quality includes cognitive problems, mood alterations, increased depression, increased irritability, reduced work performance, reduced motivation, increased safety risks, and physiological changes. Aim: To determine the baseline level of sleep quality and work performance of shift work nurses in intensive care units, and to examine the correlation between sleep quality and work performance at a government hospital in the Kingdom of Bahrain Methodology: The Pittsburgh Sleep Quality Index (PSQI) and Nurse Work Function Questionnaire (NWFQ) were used in a cross-sectional survey by simple random sample of 200 nurses working in five intensive care units in one government hospital in Bahrain (NWFQ). For data analysis, descriptive statistics, t tests, ANOVA, Pearson's correlation, and stepwise regression were used. Results: There was a high prevalence of poor sleep quality (89%) with a mean (SD) of 13.6 (± 4.9), It was statistically significant with nurse performance level. The Nurse work functioning questionnaire had an overall mean (SD) of 56.3 (±22.5). Sleep quality is comprised of seven components: sleep latency (P=0.758), subjective sleep quality (P=0.530), daytime dysfunction (P=0.112), sleep disturbances (P = 0.833), habitual sleep efficiency (P=0.792), sleep duration (P=0.801), and use of sleeping medication (P = 0.840) were found to be statistically significant predictors of nurse work performance, Along with shift work (P <0.0001), Female nurses (P = 0.010) and having a children (P = 0.043), nurses' educational level (P <0.0001), and nurses' designation (P <0.0001). Conclusion: The study results suggested that poor sleep quality may lead to lower nurse performance and very persistently poor sleep quality among shiftwork critical care nurse nurses . There was a statistically significant difference between critical care nurses who did one shift and those who did two shifts, and nurses who worked three shifts had even lower sleep quality. In addition, critical care nurses' performance was impaired more significantly with more shifts worked. Practice Implication: little is currently known regarding the relationship between sleep quality and work performance in Bahraini nursing literature; this study intended to fill the gap. Worksite training and education services are needed to detect, prevent, manage, and follow up with nurses who have poor sleep quality to maintain nurses' well-being and health, this increased quality of nursing work performance. Keywords: Sleep Quality, Work Performance, Critical Care Nursing, Shift Work Schedule