Cognitive-based human errors have major contribution to performance and safety in working environment. This study designed to develop a measurement tool in order to evaluate this type of errors in the occupational settings. An Occupational COGNITIVE FAILURE QUESTIONNAIRE (OCFQ) was developed. Content validity of the OCFQ was performed using a quantitative approach. Reliability of QUESTIONNAIRE was assessed by internal consistency and test-retest methods. A preliminary list of 35-items was prepared as a starting point. After evaluation of validity, five items were rejected. The new measurement instrument with 30-items was finally developed. The content validity index (CVI) for the final OCFQ was found acceptable (CVI= 0.7). Results show that final OCFQ was internally consistent (a= 96) and intraclass correlation coefficients (ICC) was 0.99. Measurement of COGNITIVE FAILURE in the WORKPLACE requires a valid and reliable tool. In respect to probable outcomes of COGNITIVE FAILURE s occurrence at work, the present study suggested that OCFQ would be a useful instrument for measurement of COGNITIVE FAILURE in the working environment.