BackgroundDespite policy and practice mandates for patient involvement, people with serious mental illness often feel marginalised in decisions about antipsychotic medication.AimsTo examine stakeholder perspectives of barriers and facilitators to involving people with serious mental illness in antipsychotic prescribing decisions.MethodSystematic thematic synthesis.ResultsSynthesis of 29 studies identified the following key influences on involvement: patient's capability, desire and expectation for involvement, organisational context, and the consultation setting and processes.ConclusionsOptimal patient involvement in antipsychotic decisions demands that individual and contextual barriers are addressed. There was divergence in perceived barriers to involvement identified by patients and prescribers. For example, patients felt that lack of time in consultations was a barrier to involvement, something seldom raised by prescribers, who identified organisational barriers. Patients must understand their rights to involvement and the value of their expertise. Organisational initiatives should mandate prescriber responsibility to overcome barriers to involvement.Declaration of interestNone.