This qualitative research was designed to understand how the social integration process in the workplace unfolds with adults who have intellectual disabilities. Participant observation and interviews permitted an in-depth examination of 10 integration situations within a company, with regard for the actions and perceptions of the stakeholders. Analyses revealed various intertwined processes, in which the focus persons and their colleagues together sought an optimal adjustment, or coadaptation, with support from a job coach. The study of these interactive processes led to the emergence of a theory of coadaptation, a process that defines and builds social and professional integration. This theoretical development revisits the interactive process within the socioecological perspective of disability and the concept of support and its assessment.