This article presents an outline of a theory of stigmatization, consisting of theoretical propositions and a graphic model, which can help describe and explain stigmatization processes in the personal social services. The building blocks of the theory originate from existing theories and previous empirical research including our own study of stigmatization processes among social workers in Sweden and the United States. Pattern matching methodology was key to identifying a need for a new theory. Contributions to existing theory and potential implications for policy and practice are discussed, especially in relation to social work in the personal social services. The outlined theory contributes to existing stigma theory in several ways, of which three key findings are highlighted. The theory suggests: 1) that stigmatization processes can go in several directions, sometimes simultaneously; 2) that stigmatization processes can involve mutual reinforcement which can develop into a negative spiral; 3) that stigma can be placed upon social work as an institution. The outlined theory can be used as a starting point for analysing stigmatization processes in social work in several contexts, such as different institutional or organizational settings. We argue that existing stigma theory does not always provide sufficiently deep or specific explanations that are appropriate for the uniqueness of different settings. Thus, there is a need for a theory that is more precise and adapted to such a setting. The framework can be useful for researchers and university students that need a theory when studying stigma processes in social work practice.