<p>Biodegradable alloys in orthopedic implant applications avoid revision surgeries; these alloys need mechanical properties akin to human bones and desirable degradation rates. This study investigates how Zn and Ca content influences the mechanical and degradation properties of as-cast Mg–Zn–Ca alloys. The study involved six alloys with two different Zn contents (3 and 5 wt.%), each having three different Ca contents (0, 0.3, and 0.5 wt.%). This manuscript describes the structural and mechanical characteristics and <i>in vitro</i> degradation (in simulated body fluid) of these alloys. The ultimate tensile strength and elongation of each 0.3 wt.% Ca alloy are greater than those of the corresponding 0.5 wt.% Ca alloy (MZC33 &gt; MZC35 and MZC53 &gt; MZC55; the first digit represents the Zn wt.% while the second digit denotes 10 times the Ca wt.%). The observed changes are explained on the basis of phase composition, microstructural changes, secondary phase distributions, etc. The degradation of the alloys with 3 wt.% Zn increased with Ca content in potentiodynamic investigations. Amongst the alloys with 5 wt.% Zn, the MZC53 alloy (5 wt.% Zn and 0.3 wt.% Ca) had the lowest corrosion rate; these alloys, in the order of increasing corrosion rate, are: MZC53 &lt; MZC50 &lt; MZC55. The degradation in the immersion studies is higher for each 0.3 wt.% Ca alloy than for the corresponding (same Zn content) 0.5 wt.% Ca alloy (MZC33 &gt; MZC35 and MZC53 &gt; MZC55). Discrepancies in the long-term immersion studies vis-à-vis the potentiodynamic polarization studies are elucidated in terms of time, ion accumulation, and associated reactions. The authors suggest post-processing of the alloys to enhance the properties to suit orthopedic implant requirements.</p>