Strontium (Sr2+) is the active substance of pharmaceuticals used for reducing fracture risk in osteoporotic patients. Lately, Sr2+ is combined with biomaterials to enhance osteogenesis, which has been vaguely studied considering periodontal tissue regeneration. Despite extensive use, the mechanisms of action of Sr2+ are not fully understood. The present study assesses the impact of Sr2+ on primary human periodontal ligament cells (PDL cells) and human osteoblasts in regard to proliferation and pro-osteogenic activity. Cultured human PDL cells and osteoblast cell lines MG63 and hFOB 1.19 were treated with SrCl2 (0.1-10 mM) or vehicle for 72 h. Cells were counted manually using a Bürker chamber. Total protein content was determined by colorimetric analysis using Bio-Rad protein assay. Alkaline phosphatase activity was determined enzymatically and normalized to total protein content. SrCl2 had no significant effect on PDL cells (p>0.05), but a tendency towards induced osteogenic characteristics was observed. In contrast, 5 mM SrCl2 enhanced total MG63 cell protein content by 37% (p<0.01), compared to vehicle, whereas a lower concentration (0.1 mM) did not. 5 mM SrCl2 increased MG63 cell number by 38% (p<0.001), while a higher concentration (10 mM) did not have a significant additional effect over the 5 mM (+54%, compared to vehicle, p<0.05). The results demonstrate that 72 h administration of ≥ 5 mM SrCl2 exerts a pro-proliferative effect on human osteoblast-like MG63 cells and display a tendency to induce osteogenic characteristics in primary human PDL cells.