In December 2020, WPF engaged Mathematica to carry out the Informal Child Care in Philadelphia research project to learn about the city’s informal care landscape and the networks and supports available to informal providers. The project also sought to identify opportunities for enhancing the quality of the care. COVID-19 provided an additional impetus to better understand issues relevant to informal care, with Philadelphia’s formal child care centers closed or operating with reduced capacity. This brief summarizes findings from several formative evaluation activities that took place from February to August 2021.  (author abstract)