Macrophage and osteoclast proliferation, differentiation and survival depend on colony-stimulating factor-1 receptor (CSF1R) signaling. Human homozygous CSF1R mutations are associated with flattened and diffusely dense vertebral bodies, metaphyseal and epiphyseal osteosclerosis and thin cortices. Studies of the phenotypic consequences of Csf1r knockout (Csf1rko) in mice were limited by early postnatal lethality. We recently generated Csf1rko rats which are viable as adults on an outbred background. Here, we explore Csf1rko impacts on postnatal bone development. Csf1rko rats are indistinguishable from littermates at birth but exhibit postnatal growth retardation. However, Alcian blue-Alizarin red staining of newborn skeletons already showed delayed mineralisation of small paw bones and digits. At 1 week, osteopetrosis was evident. The muscle fibers formed around bones were reduced in diameter. By 3 weeks, mutant rats had intriguing site-specific skeletal defects: profound delay in ribcage ventral segment mineralisation, vertebral body development, secondary ossification center formation in long bones and digits, and subarticular ossification of small paw bones and carpal-tarsal bones. At 7 weeks, the cranial case of mutants lacked calcification and suture closure was impaired. All these skeletal features were shared with human CSF1R mutation. We examined macrophage and osteoclast distribution by immunohistochemical localisation of IBA1 and TRAP, respectively. Abundant macrophages in the paw, vertebral body and hind limbs were detected in 1- and 3-week-old wild-type rats and were almost absent in Csf1rko. Osteoclasts were also undetectable. Macrophages were partly restored in 7-9-week-old Csf1rko rats, but osteoclasts remained absent. Wild-type bone marrow cell transplantation into unconditioned 3-week-old Csf1rko rats reconstituted macrophages and osteoclasts, reversed skeletal abnormalities as early as 7 weeks post-transplant, promoted skeletal and somatic growth, and long-term survival. Our findings have important implications for understanding the consequences of CSF1R mutation for the human skeleton and reveal the therapeutic potential of targeting the CSF1-CSF1R axis in related bone diseases.