We study public assistance participation among homeless shelter users, characterizing the trajectories of public assistance receipt for individuals before and after they enter shelters and analyzing the influence of public assistance participation on subsequent shelter use. Our analysis identifies three distinct groups of shelter users based on personal characteristics and prior patterns of public assistance use. These groups are differentiated by their patterns of no use, increasing use, and high use of public assistance. For all three groups, increased participation in public assistance programs following the first observed homeless shelter entry reduces subsequent shelter use. The analysis draws attention to the potential role of public assistance programs and strengthened coordination of services for the prevention of homelessness.