This study contributes to the emerging research literature on science, technology, engineering, and mathematics (STEM) support and persistence activities among urban teenage African American and Latina girls. We present three case studies of girls who participated in an afterschool STEM curriculum. Our within- and cross-case analyses focused on how various supports explained girls’ STEM persistence and career plans. Findings highlight the important role that parents played in supporting girls’ persistence and career interests across settings. These findings emphasize the need for research that spans settings to better understand the interplay of support networks that influence girls’ STEM interest and persistence.