This thesis aims to investigate and to analyze the legal regulation regarding the psychosocial working environment for temporary agency workers. The complexed employment relationship of the temporary agency workers involves a shared responsibility for the work environment between the staffing agency and the customer company in order to secure a satisfying work environment for the temporary agency worker. However, the triangular relationship between the parties may result in an indistinct division of responsibilities concerning the work environment. This thesis will therefore study the demarcation of the shared responsibility for the work environment through a legal inquiry of the current legislations in the field, which will be complemented with a legal analyze of the practical consequences of the psychosocial working environment for the temporary agency workers. The legal inquiry showed that neither EU-, nor national legislation, sets out a distinct division of responsibilities concerning the work environment and it is therefore up to the staffing agency and the customer company to cooperate and to distribute the legal responsibilities between one another. The legislation does however regulate that the customer company ́s work environment responsibility is limited to the actual work that the employee performs under their management and control. The customer company does also have an obligation to involve the temporary agency workers in their systematic environment work. The staffing agency, which is the employer of the temporary agency workers, has the ultimate responsibility for the work environment and is therefore responsible the long-term aspects of the environment work.