Well-being at work is one of the factors determining healthy work conditions and is perceived by workers as a positive psychological state. In this study, the concept of well-being at work was used together with occupational functionality (i.e., current health state, current work environment, and barriers/facilitators to implementing well-being at work), occupational risk perception, and proactivity/negotiations held by workers to improve working conditions. In this context, the objectives were to identify the socio-demographic and occupational characteristics independently associated with levels of well-being at work of the multidisciplinary PHC health team; detect barriers or facilitators resulting from the attitudes of colleagues, community members, and managers that influence the well-being at work of the multidisciplinary health team; and identify with whom and what reasons led health workers to become proactive and negotiate improved working conditions. This cross-sectional study addressed 338 health workers from the multidisciplinary teams of PHC outpatient services in the extreme south of Brazil. Multivariate linear regression models were adopted to analyze data. The results show various independent associations with levels of well-being at work. Nursing workers (technicians and nurses) more frequently expressed job commitment and job satisfaction. Difficulties in solving problems and performing work routines, and co-workers' attitudes directly influence the well-being of the PHC team members. Risk perception (physical and chemical) also influences well-being. Negotiations in which PHC managers engaged to improve working conditions appeared as a significant predictor of job commitment, job satisfaction, and job involvement. The results reveal that well-being at work is an important indicator of the potential of workers' proactivity in negotiating improved working conditions.