Out-of-school time (OST) programs like the Coastal Ecology science camp can positively influence science identities, particularly for youth from groups historically underserved and underrepresented in science, technology, engineering, and math (STEM). OST STEM programming gives youth opportunities to learn science outside the formal classroom in such settings as afterschool programs, science camps, outreach programs, internships, and scouting. OST science programs often do not formally assess participants or assign grades. They provide opportunities for authentic, meaningful learning that may be more comfortable for some youth than school curricula. Further, OST programs may give youth access to resources and to scientific practices and tools not typically available in classrooms. This access may be especially important for youth from underresourced schools. Many programs allow youth to explore science in ways that support their identities. The study presented in this article explored how the Coastal Ecology science camp helped participants, specifically girls, develop science identities. It also studied how the girls' social interactions supported their identities as learners of science.