Objective: Maintaining safe physical distance is paramount to slowing the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)/coronavirus disease 2019 (COVID-19), particularly indoors (e.g., while shopping). We used a health message intervention to motivate grocery store customers to engage in distancing behavior. Method: In an online experiment (N = 206) and a field experiment (N = 268; preregistered on OSF), we used a 2 × 2 between-subjects design and manipulated health messages (a) as gain-framed ("to foster health") versus loss-framed ("it could be deadly") and (b) as targeting different beneficiaries (customers themselves versus fellow citizens). In the field experiment, observers rated customers' distancing behavior during a random confederate encounter and a subsequent interview. We assessed customers' perceptions of risk and worry, perspective-taking, and state optimism as concurrent psychological processes to investigate customers' distancing behavior in correlational mediation analyses. Results: Contrary to previous research, the intervention was more effective when pertaining to customers themselves than to their fellow citizens (Experiments 1-2). In addition, loss-framed messages were more effective than gain-framed ones (Experiment 2). The former behavioral effect was accompanied (and statistically mediated) by a concurrent psychological increase in customers' perceived risk and worry. Conclusions: Owing to their low cost and easy implementation, health messages constitute a promising means to promote physical distancing. Our results show that their effectiveness significantly depends on the framing and target of the health behavior.