Few studies have examined temporal changes in the contribution of psychosis to homicide offending. This research examines whether the incidence and the proportion of people with schizophrenia spectrum disorders, compared to all homicide offenders, have changed over a 20-year period in Sweden. All homicide offenders in Sweden from 1987 through 2006 were identified in the National Register for Criminal Convictions and linked on an individual level to the Central Archive of the National Board of Forensic Medicine, where data concerning individuals subjected to a forensic psychiatric examination in Sweden are registered. Offenders with a diagnosis of a schizophrenia spectrum disorder (F20-F29) formed the subgroup of offenders with psychosis. While the overall incidence of homicide did not change over time, both the incidence and the proportion of offenders with schizophrenia spectrum disorders decreased somewhat in relation to all homicide offenders. Although offenders with a schizophrenia spectrum disorder still comprise a disproportionately large share of all homicide offenders, their contribution to the overall incidence of homicide is at least not increasing in Sweden. Yet, it remains a significant problem that needs to be addressed by clinicians and researchers.