Beginning in 2005, researchers at Kaiser Permanente Northern California (KPNC) Division of Research developed the Research Program on Genes, Environment, and Health (RPGEH), a research resource of linked biospecimens, health surveys, and electronic health records on more than 200,000 adult KPNC members. This study examined multiple stakeholders’ values and preferences regarding protection of participants’ privacy and wide sharing of participant data by RPGEH. We conducted 45 semi-structured interviews in person or via phone and two focus groups with seven stakeholder groups, including RPGEH participants and decliners who are KPNC members, KPNC research scientists, external scientists, leadership, Human Subjects Research Protection Program staff, and RPGEH Community Advisory Panel members. Three major themes emerged related to: (1) perceived individual and social harms associated with data sharing; (2) concerns to address when governing access to RPGEH data; and (3) impact of a blurred boundary between research and clinical care in the context of biobanking. The study results were considered in the development of RPGEH data governance and motivated the inclusion of KPNC Community Advisory Panel members and ELSI experts on committees that evaluate data access proposals. Our findings can help inform other biobanks going through similar processes developing data sharing and access policies.