The majority of contemporary occupations involve tasks requiring significant mental effort and ability to handle simultaneous work. Previous studies have investigated effects of multitask work on operator performance and cognitive responses. However, in real workplace settings, these tasks usually involve managing work with varying levels of demand. Consequently, it is essential to investigate changes in task performance and levels of mental workload experienced by operators. This study was conducted to examine the effects of multitasking under various conditions, including different levels of stressors, task sequences, and durations—hence mimicking real-world work scenarios—on performance, workload perception and physiological signals, including cardiac and electrodermal activity. The findings indicate that optimizing workload intensity, adjusting task sequences, and implementing pre-task training sessions can enhance multitasking performance and reduce perceived workload. These insights offer practical guidelines for designing effective multitask work environments.