Many health problems arise from mental, neurological, and substance use disorders. These disorders are highly prevalent and complex and contribute to poor health outcomes, premature mortality, security risk, social isolation, and global and national economic loss. Mental health and substance use disorders are among Australia's top four causes of disease burden. Our objective was to investigate and synthesize contemporary literature regarding factors that influence nurses' delivery of integrated care to people with combined mental health and substance use disorders within mental health services. We systematically searched five electronic databases with a limit on publications from 2009 to 2021. The search yielded 26 articles. Following thematic analysis, three themes were identified: individual nursing characteristics, nursing education, and professional development characteristics, and organizational factors. This study reveals that there is a fundamental absence of adequate integrative models of care within mental health services to enable the optimal nursing care of people with combined mental health and substance use disorders. Future research is needed to determine nurses' perceptions and factors influencing their role as participants in integrative care. The results could strengthen nurses' contributions in developing/adopting integrative models of care and contribute to clinical, educational, and organizational development.