Magnesium-based alloys are relatively new materials for orthopedic implants. One common component that makes magnesium-based alloys biocompatible and chemically stable is the addition of minor compositions of rare earth metals like yttrium to anchor other chemically active components. From an orthopedic perspective, two goals are of primary concern. One is sufficient mechanical support to stabilize the fracture and reduce inflammation. Another is assistance for the transition of osteogenesis and intramembranous ossification for bone production and remodeling. To attain both goals and further improve the current magnesium-yttrium alloys, adding extra ingredients to improve osseointegration is a common and effective approach. By the nature of bone chemistry, calcium is the top choice as calcium is the key element in maintaining bone integrity and biochemical metabolism. In this study, the mechanical behaviors of a calcium-added magnesium-based alloy (Mg-Y3.5 wt%) are investigated by experiments. This inventive idea for the natural source of calcium is obtained from chicken eggs due to their (1) cost-effective and abundant availability, and (2) naturally synthesized calcium carbonate along with a minor content of organic materials. The fabrication processes involved are the ball-milling of eggshells as an additive at 1, 3, and 5 wt%. into magnesium-yttrium alloys and resistance casting to form composites. Material characterization includes microstructural analysis by X-ray diffraction, morphological/elemental analysis via optical microscopy, field emission scanning electron microscopes, energy-dispersive X-ray spectroscopy, mechanical properties by uniaxial compression and Vickers microhardness tests. Experimental results supplemented by statistical and finite element analysis indicate that the new composite exhibits enhanced ductility; and the 3 wt% eggshell-added alloys show better reinforcement of mechanical properties among all samples with an ultimate compression strength of 161.19 MPa, maximum elongation of 17.53 %, and hardness of 457.48 (N/mm2). Note that the comparable mechanical strength of the composite to that of human bones could reduce the stress shielding on bones and further help the process of bone remodeling.