Aim: Shared decision making for adults with severe mental illness has increasingly attracted attention. However, this concept has not been comprehensively clarified. This review aimed to clarify a concept of shared decision making for adults with severe mental illness such as schizophrenia, depression, and bipolar disorder, and propose an adequate definition. Methods: Rodgers' evolutionary concept analysis was used. MEDLINE, Psy-chINFO, and CINAHL were searched for articles written in English and published between 2010 and November 2019. The search terms were "psychiatr*" or "mental" or "schizophren*" or "depression" or "bipolar disorder", combined with "shared decision making". In total, 70 articles met the inclusion criteria. An inductive approach was used to identify themes and sub-themes related to shared decision making for adults with severe mental illness. Surrogate terms and a definition of the concept were also described. Results: Four key attributes were identified: user-professional relationship, communication process, user-friendly visualization, and broader stakeholder approach. Communication process was the densest attribute, which consisted of five phases: goal sharing, information sharing, deliberation, mutual agreement, and follow-up. The antecedents as prominent predisposing factors were long-term complex illness, power imbalance, global trend, users' desire, concerns, and stigma. The consequences included decision-related outcomes, users' changes, professionals' changes, and enhanced relationship. Conclusions: Shared decision making for adults with severe mental illness is a communication process, involving both user-friendly visualization techniques and broader stakeholders. The process may overcome traditional power imbalance and encourage changes among both users and professionals that could enhance the dyadic relationship.