The spread of Asian chestnut gall wasp (ACGW) Dryocosmus kuriphilus Yasumatsu (Hymenoptera Cynipidae) is an emergent constraint factor for Italian chestnut stands and orchards, considering its potential to reduce plants vigour and chestnut production. Biological control with the introduced parasitoid Torymus sinensis Kamijo (Hymenoptera Torymidae) is being performed in Italy, but search for autochthonous antagonists appears as an urgent topic to improve strategies for the protection of chestnut stands. This study reports the first finding and the parasitic action of fungi detected in necrotic wasp galls in some stands of Castanea sativa Mill. in Tuscany and Piedmont regions: Fusarium incarnatum-equiseti species complex (FIESC) 25-b and 3-b, Alternaria alternata (Fr.) Keissl., Botrytis sp. were identified. After fungi were isolated, artificial inoculations were carried out in field: six selected strains were tested on 10 healthy galls each (two strains of FIESC 25-b, one of FIESC 3-b, two of Botrytis spp., and one of A. alternata). Dead adults of wasp were found inside 47% of the 60 treated galls, and the highest lethal effect was produced by the Fusarium strains (60-70%) and by one strain of Botrytis spp. (60%). Moreover mycelial linear growth in plate of the six strains was tested on gall extract agar medium (GEA), and compared to that on PDAmb and water-agar: on GEA the significantly (p < 0.001) highest linear growth was recorded for three strains after 4 days and four strains after 8 days. Isolation of Fusarium mycelia from bodies of dead adults, inside galls both naturally and artificially necrotized, emphasises their infective ability. In conclusion the two Fusarium species show interesting perspectives and verifiable opportunities for ACGW biocontrol.