Current studies indicate that biodiversity and pedodiversity may have similar patterns, for example diversity–area relationships. This study examines pedodiversity and biodiversity–area relationships on a global scale using countries as spatial units. The Food and Agricultural Organization (FAO) soil database and International Union for the Conservation of Nature–World Commission on Protected Areas (IUCN–WCMC) biological datasets have been used in this analysis. The results show that biodiversity of biological target groups (the number of species of vascular plants, amphibians, reptiles, birds, mammals, and the total number of species of vertebrates) and pedodiversity (the number of pedotaxa or soil types at the second level of FAO classification) conform to the power law. The two types of diversity are strongly correlated at the global level. When a country has high pedodiversity it has also high biodiversity, and since pedodiversity may be interpreted as an expression of environmental heterogeneity in terms of geological parent material, geomorphology, and climate of a given area, this result suggests that the biodiversity of a country depends both on the extent of its area and on its environmental heterogeneity. We are conscious of the limitations of the results due to the inherent imprecision of the data set used for this study; however, we think that this analysis could motivate interest in continuing to study the pedodiversity–biodiversity relationships with a new pedotaxonomy that would take into consideration the deep regolith layers.