Background- Nurse fatigue is a huge threat to patient safety; hence it is important to investigate the main latent variables leading to nursing fatigue. Aims- The aim of the present study is (1) to measure the neurophysiologic symptoms of fatigue in ICU nurses. (2) to identify the main latent variables of nursing fatigue among ICU nurses. (3) to find out the association of selected socio demographic characteristics of the ICU nurses with fatigue level. Methods- Non-experimental research design, active participated respondents were 132 ICU nurses selected from 4 private hospitals. Data were collected using a self administered questionnaire (2 sections) i.e. socio-demographic variables and fatigue scale. Results and Conclusions- Mean value 99.8 indicate fatigue level of nurses to a great extent, Chi square value shows significant (P ≤ 0.05) association with age, sex and years of experience. Multifactorial analysis was applied; main latent variables of fatigue level with high loading factors were related to fatigue is symptoms of tiredness. Findings shows that nurses experiences fatigue to a great extent and main variables related to fatigue is symptoms of tiredness.