Creating a pro-regenerative immune microenvironment around implant biomaterial surfaces is significant to osseointegration. Immune cells, especially macrophages that participate in the osseointegration, including osteogenesis, osteoclastogenesis, and angiogenesis, should be considered when testing biomaterials. In this study, we immobilized an antimicrobial peptide GL13K with immunomodulatory properties onto a titanium surface via silanization. The modified surfaces show good biocompatibility with bone mesenchymal stromal cells (BMSCs), human umbilical vein endothelial cells (HUVECs), and RAW264.7. By co-culturing BMSCs with RAW264.7, we found that the GL13K-coated titanium surfaces could promote late-stage osteogenesis as demonstrated by the upregulated expression of recombinant collagen type I alpha 1 (COL-1α1) and more extracellular matrix mineralization, while the early phase remained unchanged. The surfaces inhibited the osteoclastogenic differentiation of RAW264.7 cells by restraining nuclear factor-activated T cells, cytoplasmic 1 (NFATc1), the main factor of the receptor activator of nuclear factor-κ B, and the receptor activator of the nuclear factor-κ B ligand signaling pathway, from entering the nucleus and further reduced the expression of the activating osteoclastogenic tartrate-resistant acid phosphatase gene. Moreover, the GL13K-coated titanium surface demonstrated significant promotion of angiogenesis differentiation of HUVECs as indicated by the upregulated expression of essential angiogenesis function genes, including hypoxia-inducible factor-1α, endothelial nitric oxide synthase, kinase insert domain receptor, and vascular endothelial growth factor A (HIF-1α, eNOS, KDR, and VEGF-A). Taken together, these results demonstrated that the GL13K coating had properties of osteogenesis, angiogenesis, and anti-osteoclastogenesis via its immunomodulatory potential.