Abstract: Taking two cobalt-related sites in different districts/counties of a city in Shandong Province as examples, this study investigated the spatial distribution patterns and correlations of soil cobalt and fully identified the high-cobalt geological background originating from regional volcanic rock parent materials. We applied the background reference area method and multiple lines of evidence (MLOE) analysis to determine the upper limits of soil cobalt background values, and then conducted a comparative analysis. The results showed that anomalously high cobalt values in Site 1 were mainly distributed in the completely weathered and strongly weathered layers, where siderophile elements displayed good correlations, likely derived from the same parent material. In Site 2, anomalously high cobalt values predominantly occurred in the miscellaneous fill layer, and the suspected introduction of exogenous cobalt weakened the correlations among siderophile elements. The upper limits of the soil cobalt environmental background values obtained by the background reference area method and MLOE analysis were 82.5 mg/kg and 78.9 mg/kg for Site 1, and 36.7 mg/kg and 44.4 mg/kg for Site 2, respectively, all substantially higher than the regional soil cobalt background values reported in the literature. For the same site, the statistical characteristics of the background data derived from different methods were similar, and both methods could serve as effective approaches for distinguishing background data from anthropogenic inputs. This study can provide a reference for determining the soil environmental background values at similar sites and establishing local standards.