A study analyzed the effects of the Affordable Care Act (ACA) Medicaid eligibility expansion on enrollment among individuals experiencing homelessness in New Jersey and Pennsylvania. Using administrative data from January 2011 to December 2016, researchers performed interrupted time-series analyses, linking Homeless Management Information System data to monthly Medicaid enrollment files for non-elderly adults. The findings indicated that Medicaid enrollment increased by 7.5 percentage points in New Jersey and 8.5 percentage points in Pennsylvania following the ACA expansion. Additionally, enrollment trends rose by 0.6 percentage points per month in New Jersey after the expansion. Those who utilized homeless services, such as shelters or outreach assistance, showed a significantly higher likelihood of enrolling in Medicaid, particularly with multiple months of service use. However, the positive effects of the ACA on enrollment diminished back to pre-ACA levels by the end of 2016. The results suggest a need to explore how relationships between clients and staff in homelessness assistance programs can be leveraged in future health policy efforts to improve Medicaid enrollment for this vulnerable population.