Beta-lactoglobulin (Blg) is the most abundant whey protein in the milk of ruminant animals, yet its physiological function is yet to be confirmed. It is not present in human milk and has been identified as one of the main immunogenic proteins in cow milk. Goat milk appears to be less allergenic and more easily digested than cow milk. As Blg is the most abundant whey protein differences in its structural, physicochemical and dynamic properties may be responsible for some of the differences seen between these milks. We have successfully solved an ultra-high resolution crystal structure of caprine Blg and collected analytical ultracentrifugation and small-angle X-ray scattering data. There are subtle differences between the orthologs and while both bovine and caprine Blg are dimeric in solution and crystalline states, our data suggest a flexible arrangement of subunits within the dimer. These structural findings will direct further studies into the dynamics of the protein and its binding behaviours with other components in milk, which may provide insight into the differences between these species’ milks and potentially the physiological role of this enigmatic protein.