This paper investigates how business angels (BAs) embody core identity practices within business angel networks (BANs) and, in doing so, shape Berlin’s entrepreneurial ecosystem (EE). Departing from entrepreneur-centric narratives, the study foregrounds early-stage investors as sociocultural actors who participate in and reinforce the ecosystem’s informal institutions. Drawing on entrepreneurial ecosystem theory, organizational culture, and social identity theory (SIT), the paper explores how norms, values, and group affiliations influence investment behavior. Here, SIT offers a valuable psychological lens to understand how group membership shapes perceptions, behaviors, and decision-making by aligning individual self-concept with collective norms and values. Through six qualitative interviews with BAs and BAN representatives, the findings highlight a tension between individual agency and collective identity. While BAs frame their decisions as objective and experience-based, their practices are shaped by cultural fit, symbolic boundaries, and the desire for legitimacy within the network. BANs, in turn, institutionalize these informal codes, reinforcing homogeneity while projecting openness. Ultimately, the paper argues that belonging to a network matters not only structurally but as a cultural field that shapes perception, enforces norms, and reproduces dominant ecosystem values. By tracing these informal logics, the study contributes to emerging research on the sociocultural foundations of entrepreneurial ecosystems and opens space for future inquiry into the cultural reproduction of power and inclusion within these systems.