The present research uses a pre-post quasi-experiment to investigate the effect of a manager-based intervention on organization-level safety climate promotion by managers' safety management actions, which is operationalized as safety management by walking around (SMBWA). Considering that the highly observable and consistent management actions in SMBWA are effective signals to demonstrate managers' commitment to safety and can provide favorable information concerning safety climate, we hypothesized that the SMBWA would improve the organization-level safety climate. In addition, we argued that the intervention could bring other benefits to employees, that is, a positive organization-level safety climate boosted by SMBWA, as a form of organizational resource, could reinforce safety motivation and alleviate burnout, which, in turn, could benefit safety behavior at the individual level. A total of 19 working sites with 224 employees from a Chinese petrochemical organization participated in our study (n = 119 in 10 experimental groups; n = 105 in 9 control groups). The results of the linear mixed models indicated that the organization-level safety climate, individual-level safety motivation, burnout, and safety behavior significantly changed in the experimental group but not in the control group. Furthermore, the multilevel path modeling results showed that the relationship between SMBWA and safety behavior was mediated by organization-level safety climate (first-stage mediator), and safety motivation and burnout (second-stage mediators). The theoretical and practical contributions to safety climate intervention research and workplace safety improvement are discussed.