Many accidents occur due to various factors when undertaking construction projects. One of the most important achievements when undertaking a construction project is to accomplish the project without major accidents. This paper studies the effect of stress, fatigue and workload on construction contract worker in term of their safety performance results using the Situation Awareness Rating Technique (SART), with reference to how it relates to the root causes of accidents. Investigating the factors associated with accidents helps to identify and minimize the associated mistakes or causes and reduce or avoid accidents and improve safety performance in construction projects. Data were collected using a SART survey of employee of 18 contractors working on construction of electrical substations in the western area of Saudi Arabia. It was found that most accidents occurred at the worker level because of their lack of awareness and training. It is apparent that SART affects the safety performance of contractors and it varies with the position, age and experience of workers. To implement a safe working environment free of accidents, it is necessary to improve all job levels according to their insufficient area and activate a full safety management system with periodic reviews to improve it and make it more effective.