The European chestnut (Castanea sativa Mill.) is a specie with great economic importance in Europe that have been present for thousands of years. In Portugal, the chestnut helps to maintain a positive trade balance, by contributing to the gross national product (GDP). One of the biggest threats for the chestnut is the ink disease caused by Phytophthoracinnamomi, this disease is problematic to chestnut crop with a damaging impact. Silicon (Si) is classified as a beneficial nutrient, having the ability to make plants more resistant to attacks by pathogens. Studies on the effect of silicon on chestnut are practically non-existent, so the aim of this study was to evaluate the impact of silicon in the resistance of chestnut plants to P. cinnamomi. The plants were treated by 0 mM, 5 mM, 7.5mM and 10 mM SiK® with the analyzed mad at 0, 15 and 30 days after inoculation by P. cinnamomi. These findings showed that the Si-treated plants had higher survival rate resulted from the presence of phytoliths in root tissues, that acted as a mechanical barrier reducing the development of pathogenic structures and they arealso associated with the improvement on antioxidant activity through the increase of CAT and SOD, higher values of total phenols compounds and less oxidative damage. The presence of Si in PDA medium reduced the growth of P. cinnamomi all over the time, presenting high PI. This work shows that the Si fertilization in chestnut plants contributes to increase the resistance against P. cinnamomi infection.