Based on the social cognitive model and on the psychology of working theory, this research aims to study the job and life satisfaction of apprentices, considering proactive personality, person-supervisor and person-group fit, occupational self-efficacy, and decent work as antecedents. The participants were 530 Swiss apprentices enrolled in a three-year VET program with the Federal VET Diploma. The results show that proactivity is directly linked with person-supervisor and person-group fit, occupational self-efficacy, and job and life satisfaction. Decent work is related positively with job satisfaction. Person-supervisor and person-group fit seem to directly influence occupational self-efficacy. Decent work, in turn, seems to mediate the relationship between person-supervisor and person-group fit and job satisfaction. In conclusion, this study suggests that encouraging apprentices' proactivity, person-supervisor and person-group fit at work could be crucial to improving their perceptions of decent work and increasing their job and life satisfaction.