Introduction: Nursing activities score scales are valuable instruments for assessing the quality of nursing care provided in critically ill patients and easy to use in validating nurse staffing. The aim of this study was the assessment of nursing workload (NW) as a predictive factor of mortality by using the nursing activities score (NAS) scale. Materials and Methods: In this cross-sectional study of 91 days during 2019, convenience sampling was employed to recruit 82 registered nurses (RN) from three intensive care units (ICUs) of two public hospitals with 41 beds in total. Data were collected using the NAS scale, the researcher’s observation, the information given by the staff, and the nursing care reports. Descriptive and inductive statistics were used with significance level α = 0.05. The Statistical Package for Social Sciences (SPSS 25.0) was used for analyzing the data. Results: Females were the majority of the sample (84.1%), with a mean age of 38.9 (7.7) years, 87.8% had a nursing degree from a technological educational institute (T.E.I), the average working experience was 14 (8.1) years and the ICU experience was 12.9 (8.5) years. There were 3764 daily records of NAS with an average of 54.81 (2.34) and total NAS of 756.51 (150.27). The NW of the first day’s admission in the ICU was 65.15 (13.05), NW was 13.15 h/day and the NW of patients who died was 57.37 (4.06). The optimal nurse/patient ratio (NPR) was 1:1.82, while the existing NPR was 1:2.86. The mortality rate was 28.7%. Conclusion: Although the study results did not demonstrate a significant correlation between NW and mortality, the NW in ICU appeared to be relatively higher for patients who died than for those who survived. This result may serve as an indication for a positive correlation between these two variables. In addition, NW was found to be moderate, while one ICU nurse can take care of more than one patient.