The present study aimed to synthesize and characterize diopside (CaMgSi2O6) and wollastonite (CaSiO3) nano-bioceramics via a combination of mechano-chemical and calcination processes. In vitro biomineralization and cell responses of wollastonite and diopside were performed on simulated body fluid (SBF) and MG-63 osteoblast cells. Results revealed proper tissue biomineralization of wollastonite and diopside through the generation of an apatite-like layer on the surface of nano-bioceramics. Cell responses of wollastonite and diopside eventuated non-cytotoxicity by MG-63 osteoblast cells, and their viability and cell proliferation were confirmed. Alizarin red staining of diopside and wollastonite evidenced great bioactivity and tissue biomineralization, and the ALP enzyme of diopside and wollastonite was enhanced in contact with the MG-63 osteoblast cells. Regarding the existence of Mg2+ in the calcium-silicate network and the stability network, diopside illustrated high biological and cell responses in comparison to wollastonite, and both of them were suggested as bioactive and biocompatible nano-bioceramics for biomedical applications.