For the last few decades, many studies have analysed the important influence of environmental conditions on the breeding biology of ungulates. However, with reference to Mediterranean wild boar populations, there are hardly any studies. In this paper, we will research the effect of rainfall over eight years on some reproductive variables in a wild boar population located in a Mediterranean ecosystem. Our results indicated that the percentage of pregnant females was higher in rainy years than in dry ones and females over 2 years of age significantly increased their litter size in these rainy years. In addition, dry summers and autumns determined an early rut period and a high concentration of births. However, rainfall did not influence the foetal sex ratio, although we did observe that the sex of the heaviest piglet within each litter was predominantly male, this circumstance being more significant in dry years than in rainy ones. We believe that these results could be showing the wild boar’s survival strategy in the changeable environmental conditions of Mediterranean ecosystems.