Adults with a serious persistent mental illness (SPMI) express a strong desire to work. However, they continue to experience higher levels of unemployment, barriers, and occupational exclusion that impact their vocational outcomes and choice of work. The aim of this study was to investigate the impact of co-location partnerships between adult mental health and disability employment services (DES) on employment outcomes and consumer choice of work for adults with a SPMI. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology, a systematic literature review was conducted by searching four databases. The relationship between mental health, employment, and DES was examined. Inclusion criteria were adults with a SPMI; employment services and outcomes; and job retention and sustainability. Twelve studies met inclusion criteria. All studies were peer-reviewed, Australian-based, and published between 01 January 2017 and 30 August 2021. Individual placement and support (IPS); DES practice, funding, policy, and reform within the Australian mental health system; and barriers to participation in DES were the three main themes that emerged. Findings highlight the importance of joint, co-location partnerships between mental health and employment services, including a collaborative approach to policy reform between both services, to assist adults with a SPMI to gain and sustain competitive employment. Vocational, non-vocational, systemic, and structural barriers still exist; hence, adults with a SPMI continue to face challenges with gaining and sustaining long-term employment. Hence, it is important for these partnerships to be systematically set up to support the complexity of the employment journey for adults with a SPMI.