This article presents findings from a secondary study of science capital within the context of U.S. science festivals. Drawing on attendee survey data from eleven science festivals across the United States (n = 1,645) and evaluation surveys from a statewide school-based festival program (n = 2,320), we explore the concept of science capital (i.e. science-related cultural capital, science-related social capital, and science-related behavior and practices) within science festival programs. Using linear regression, we utilize attendee demographics and event characteristics to predict shifts in science capital. Our results indicate that members of STEM minority groups (i.e. girls and women; Black/African Americans, Latino/Hispanic/Latinx, Native Americans, Native Hawaiians and Other Pacific Islanders) report greater shifts in science capital scores. Time at event and scientist interactions at the event are also associated with greater shifts in scientific cultural capital. We interpret these findings in light of Philip and Azevedo's work (2017) on out-of-school science learning and equity. As a concept, science capital offers a useful lens through which to view informal science learning, science communication, and how public science events (e.g. science festivals) play an important role in contributing to the local STEM learning ecosystem.