Background and Aim: One of the most important problems in intensive care unit is high nursing workload. High workload may lead to increased human errors, compromised quality and safety of care, and reducing quality of working life. The purpose of this study provides valid and reliable tools to assess the mental workload of the ICU nurses and also identify inducing factors that will create workload.

  Materials and Methods: This study had two phases. 1- Determine the face validity and reliability of the NASA-TLX (to assess the workload) by Backward Translation method and Cronbach's alpha method. 2–Designing the performance obstacles and facilitators questionnaire by interview and pilot study.

  Results: Face validity and reliability of NASA-TLX method was confirmed (α=0.897). The performance obstacles and facilitators questionnaire for ICU nurses provides in 53 questions and 10 subscales. Relevancy is 97% and Clarity is 96%. Overall, 90% of nurses assessment comprehensiveness of the questionnaire was very comprehensive and comprehensive.

  Conclusion : According to the results, can be used NASA-TLX method and the performance obstacles and facilitators questionnaire to assess workload of ICU nurses.