Grafting of monoacryloxyethyl phosphate onto expanded polytetrafluoroethylene was achieved using simultaneous grafting with the aim of improving the membrane wettability and mineralization capacity. This study explored the effect of adding calcium ions to the grafting solution and observed increased graft yield and wettability when compared with samples grafted in the absence of calcium ions. Fourier transform infrared spectroscopy mapping found the graft copolymer to be distributed in a patchy manner across the surface as well as throughout the membrane. Through X-ray photoelectron spectroscopy analysis, it was found that calcium ions were incorporated into the graft copolymer and could be extracted using a basic ethylenediaminetetraacetic acid solution without reduction in graft yield. This implies that the presence of calcium ions is affecting the graft yield by increasing the local concentration of monomer near the surface during the grafting process. Investigation of the mineralization capacity of the grafted membranes in simulated body fluid revealed that the increased wettability of the membranes rather than the presence of the calcium ions affected the mineralization outcome.