Background: Prior research reveals high unemployment rates among homeless young adults. The literature offers many examples of using evidence-based supported employment models with vulnerable populations to assist them in obtaining and maintaining competitive employment; yet few examples exist to date with homeless young adults with mental illness. Objective: The purpose of this study was thus to adapt an evidence-based intervention for adults with psychiatric illnesses [i.e., the Individual Placement and Support (IPS)] with homeless young adults with mental illness. Methods: Convenience sampling was used to recruit 20 homeless young adults (ages 18-24) with mental illness from the host agency. Participants received the IPS intervention over 10 months. A comparison sample was used at a separate agency of 16 homeless young adults with mental illness, who received standard agency services. Using a pre-post, self-comparison quasi-experimental design, the impact of the IPS was assessed on five employment outcomes: (1) ever-worked rate, (2) working-at-follow-up rate, (3) monthly work rate, (4) weekly work hours and (5) weekly income. Results: The IPS group was significantly more likely to have worked at some point over the 10-month study as well as to have worked a greater number of months overall. Conclusions: Findings provide greater insight into adapting, implementing and evaluating the IPS model with homeless young adults with mental illness. The study demonstrates that the IPS model is adaptable to work with homeless young adults with mental illness and is associated with successful retention and employment outcomes.