The present study investigated the impacts of mating age of gilts (A1, < 230 days; A2, 230 - 249 days and A3, 250 ≤ days) on reproductive performance and litter size of sows at farrowing to weaning. A total of 102 crossbred gilts (Yorkshire × Landrace; average days old, 90 days) were purchased from a commercial breeding company. After identification of third estrus, the gilts were artificially inseminated using semen of Duroc boars. Pregnant pigs were allotted to one of three groups including A1, A2, and A3. Experimental diets and water were fed ad libitum during each experimental period which included the first, second, and third parities. Backfat thickness (BFT) of sows was higher in A3 at farrowing in the first parity than in others. At weaning time in the second parity, sows in A3 group showed a numerically higher BFT than those in A1. There was no effect of mating age on the total number of piglets born and total weaned piglets. There was a tendency to decrease the wean-to estrus-interval in the first parity as age increased at mating. Results obtained in the present study indicate that the first mating age does not affect the subsequent parites’ reproductive performance; however, weaned to estrus interval tended to decrease in A2 at the first parity.