Whilst strontium (Sr 2 +) is widely investigated for treating osteoporosis, it is also related to mineralization disorders such as rickets and osteomalacia. In order to clarify the physiological and pathological effects of Sr 2 + on bone biomineralization , we performed a dose-dependent investigation in bone components using a 3D scaffold that displays the hallmark features of bone tissue in terms of composition (osteoblast, collagen, carbonated apatite) and architecture (mineralized collagen fibrils hierarchically assembled into a twisted plywood geometry). As the level of Sr 2 + is increased from physiological-like to excess, both the mineral and the collagen fibrils assembly are destabilized, leading to a drop in the Young modulus, with strong implications on pre-osteoblastic cell proliferation. Furthermore, the microstructural and mechanical changes reported here correlate with that observed in bone-weakening disorders induced by Sr 2 + accumulation, which may clarify the paradoxical effects of Sr 2 + in bone mineralization. More generally, our results provide physicochemical insights into the possible effects of inorganic ions on the assembly of bone extracellular matrix and may contribute to the design of safer therapies for treating osteoporosis.