Many expect genome sequencing (GS) to become routine in patient care and preventive medicine, but uncertainties remain about its ability to motivate participants to improve health behaviors and the psychological impact of disclosing results. In a pilot trial with exploratory analyses, we randomized 100 apparently healthy, primary-care participants and 100 cardiology participants to receive a review of their family histories of disease, either alone or in addition to GS analyses. GS results included polygenic risk information for eight cardiometabolic conditions. Overall, no differences were observed between the percentage of participants in the GS and control arms, who reported changes to health behaviors such as diet and exercise at 6 months post disclosure (48% vs. 36%, respectively, p = 0.104). In the GS arm, however, the odds of reporting a behavior change increased by 52% per high-risk polygenic prediction (p = 0.032). Mean anxiety and depression scores for GS and control arms had confidence intervals within equivalence margins of ±1.5. Mediation analyses suggested an indirect impact of GS on health behaviors by causing positive psychological responses (p ≤ 0.001). Findings suggest that GS did not distress participants. Future research on GS in more diverse populations is needed to confirm that it does not raise risks for psychological harms and to confirm the ability of polygenic risk predictions to motivate preventive behaviors.