Introduction: This study sought to examine the effects of helmet weight on cognitive performance and mental workload. Twenty participants were studied in 3 one-hour sessions. Methods: The study participants were requested to read and work with computers under the following 3 conditions: wearing no helmets, wearing a helmet that weighed 800 g (A), and a helmet weighing 1500 g (B). “, N-back”,task and Continuous Performance Test (CPT) were employed to assess cognitive performance. At the same time, NASA-TLX and Thermal Comfort and Fatigue Perception Scale were used to evaluate mental workload and comfort. At the end of the intervention sessions, perceived mental workload, thermal comfort, and fatigue in the head were measured. Moreover, the research participants’,cognitive performance was gauged before and after the sessions. Results: The present study findings revealed that helmet weight significantly impacted cognitive performance (P<0. 001). However, no significant difference was detected in the participants’,mental workload before and after the intervention. Conclusion: Helmet weight could affect cognitive performance. Therefore, in designing helmets, the helmet’, s weight should be considered an essential factor.