The aim of the present study was to evaluate the effects of dietary supplementation of Ca-Mg complex on the longevity and reproductive performance of sows. In total, seventy-two gilts ([Yorkshire × Landrace] × Duroc, average body weight 181 kg) were randomly allocated to 1 of 3 treatments during 4 successive parity in a 4 × 3 factorial arrangement. Treatments consisted of CON (basal diet), CM1 (basal diet -MgO - 0.3% limestone + 0.4% Ca-Mg complex), and CM2 (basal diet - MgO - 0.7% limestone + 0.4% Ca-Mg complex). A higher ( < 0.05) number of totals born and live piglets, and sows increased feed intake during gestation and lactation, increased backfat thickness, and increased estrus interval were observed ( < 0.05) during their third and fourth parity than during their first and second parity. Ca-Mg complex supplementation improved ( < 0.05) the number of total piglets during the first and second parity as well as live-born piglets during the first to third parity, reduction ( < 0.05) in backfat thickness during the third and fourth parity, a higher ( < 0.05) initial and final number of suckling piglets as well as higher weaning weight compared with sows fed CON diet during the first, second, and third parity. The average daily gain (ADG) was higher ( < 0.05) in piglets born to CM1 and CM2 sows regardless of parity. The treatment diets fed to sows lowered ( < 0.05) the duration of first to last piglet birth and placenta expulsion time compared with CON sows. A significant interactive effect ( = 0.042) between parities and treatment diets was observed for the first to last piglet birth. Thus, Ca-Mg complex supplementation by partially replacing limestone in the basal diet enhanced sow performance, specifically during their third and fourth parity, thereby improving sow longevity.