The aim of this study is to understand the effect of different mental workload on selfreported performance and job satisfaction. A questionnaire was elaborated to evaluate mental workload from theoretical model IWA (individual-workload-activity). This model is composed to three components (individual physiological, affective, cognitive and social characteristics, three dimensions of mental workload, and activity characteristics with task parameters and execution context) and presents relationships between these components. 616 participants responded to on-line questionnaire. The questionnaire, composed to 40 items, was used to evaluate 4 dimensions plus self-reported performance and job satisfaction (available resources, intrinsic workload, external workload, and germane workload) in order to test their interrelationships and their relationship with self-reported performance and job satisfaction. First, reliability and validity of the questionnaire were tested. Obtained results are in agreement with IWA model and show that germane load is observed only when operators have sufficient available resources and when tasks to perform are complex and context constrains task execution. Second, job satisfaction appears to be determined by germane load mediated by self-reported performance and organisation and social ambience at work. This study shows the relevance of considering several dimensions of mental workload and their differential effects on job satisfaction and the good psychometric qualities of elaborated questionnaire of evaluation. The questionnaire presented in this study was designed to be used in the enterprises. It seems to be a good tool to pre-diagnose job situations before a more precise analysis of work.