Based on our discovery that osteal macrophages (osteomacs) promote bone anabolism, we questioned whether osteomacs contribute to, or compensate for, osteoporosis-associated disruption of bone homeostasis. CD169 is a macrophage-restricted adhesion molecule that facilitates cell-cell interactions important in bone marrow homeostasis. We found that CD169 haploinsufficiency was associated with reduced osteomacs (-35%) and a concomitant reduction in osteoblasts (-27%), with no impact on bone-resorbing osteoclasts. Additionally, CD169-null mice had reduced trabecular bone (-32%). Together, these indicate that disruption of CD169-mediated osteomac/macrophage cell interactions disrupts bone homeostasis causing a low bone mass phenotype. We next established an ovariectomy-induced model of post-menopausal osteoporosis in C3H/HeJ mice. Reduced trabecular bone volume (-46%), thickness (-21%) and number (-23%) as well as reduced cortical thickness (-8%) with increased porosity (17.5%) at 4-weeks post-ovariectomy confirmed the integrity of this model. Moreover, high resolution micro-CT scanning revealed enlargement of cortical vascular canals post-ovariectomy - a pathological feature observed in human osteoporosis. The bone loss in our model was mediated by increased osteoclasts on trabecular (p<0.0001) and endocortical bone (p<0.0016), and decreased osteoblasts on trabecular bone (p<0.0001). While there was no impact on overall osteocyte number, the frequency of TRAP-expressing osteocytes was increased in cortical bone (p=0.0005), which is suggestive of active osteocyte osteolysis, especially when considered in the context of increased cortical porosity. Interestingly, osteomac frequency was increased on both trabecular (p<0.0001) and endocortical bone (p<0.0001) post-ovariectomy. Dual F4/80 (pan-macrophage marker) and TRAP staining indicates TRAP+ vesicles within osteomacs, suggesting osteomac role in phagocytosing extracellular TRAP. Using a refined in vivo macrophage depletion model (CD169-DTR mouse), we found that osteomac loss resulted to elevated serum TRAP (p=0.0017), further supporting osteomac role in TRAP clearance. Overall, our data support that osteomacs actively contribute to sustaining bone homeostasis and provide the first evidence of osteomac functional contribution to bone post-ovariectomy.