Large quantities of parathyroid hormone‐related protein (PTHrP) are present in the milk of various species. It has been suggested that PTHrP may play a role in neonatal calcium homeostasis. In the present study we evaluated the effect of neutralization of amino‐terminal PTHrP activity by passive immunization in 1‐day‐old mouse pups. Neutralization of amino‐terminal PTHrP activity had no significant effect on serum calcium or whole‐body calcium content in the neonatal mice. In additional studies, we demonstrated that subcutaneous administration of PTHrP‐(1–34) increased serum calcium, whereas oral administration had no significant effect in 3‐day‐old pups. The studies therefore demonstrate that the amino terminus of PTHrP may not play a significant role in neonatal calcium homeostasis. Local effects of PTHrP cannot be excluded by the results of the present study.