Relapse rates among individuals with psychotic disorders are high. In addition to the financial burden placed on clinical services, relapse is associated with worse long-term prognosis and poorer quality of life. Robust evidence indicates that stressful life events commonly precede the onset of the first psychotic episode; however, the extent to which they are associated with relapse remains unclear. The aim of this systematic review is to summarize available research investigating the association between recent stressful life events and psychotic relapse or relapse of bipolar disorder if the diagnosis included psychotic symptoms. PsycINFO, Medline and EMBASE were searched for cross-sectional, retrospective and prospective studies published between 01/01/1970 and 08/01/2020 that investigated the association between adult stressful life events and relapse of psychosis. Study quality was assessed using the Effective Public Health Practice Project guidelines. Twenty-three studies met eligibility criteria (prospective studies: 14; retrospective studies: 6; cross-sectional: 3) providing data on 2046 participants in total (sample size range: 14–240 participants). Relapse was defined as a return of psychotic symptoms (n = 20), a return of symptoms requiring hospitalization (n = 2) and a return of symptoms or hospitalization (n = 1). Adult stressful life events were defined as life events occurring after the onset of psychosis. Stressful life events included but were not limited to adult trauma, bereavement, financial problems and conflict. Eighteen studies found a significant positive association between adult stressful life events and psychotic relapse and five studies found a non-significant association. We conclude that adult stressful life events, occurring after psychosis onset, appear to be associated with psychotic relapse.