Porcine bone marrow mesenchymal stem cells (pBMSCs) have the potential for application in regenerative medicine. This study aims to investigate the effects of extracellular calcium ([Ca(2+)]o) on pBMSCs proliferation and to explore the possible underlying mechanisms. The results demonstrated that 4 mM [Ca(2+)]o significantly promoted pBMSCs proliferation by reducing the G0/G1 phase cell percentage and by increasing the S phase cell proportion and the proliferation index of pBMSCs. Accordingly, [Ca(2+)]o stimulated the expression levels of proliferative genes such as cyclin A2, cyclin D1/3, cyclin E2, and PCNA and inhibited the expression of p21. In addition, [Ca(2+)]o resulted in a significant elevation of intracellular calcium and an increased ratio of p-ERK/ERK. However, inhibition of calcium-sensing receptor (CaSR) by its antagonist NPS2143 abolished the aforementioned effects of [Ca(2+)]o. Moreover, [Ca(2+)]o-induced promotion of pBMSCs proliferation, the changes of proliferative genes expression levels, and the activation of ERK1/2 signaling pathway were effectively blocked by U0126, a selective ERK kinase inhibitor. In conclusion, our findings provided evidence that the enhanced pBMSCs proliferation in response to [Ca(2+)]o was associated with the activation of CaSR and ERK1/2 signaling pathway, which may be useful for the application of pBMSCs in future clinical studies aimed at tissue regeneration and repair.