Neofusicoccum luteum species belongs to the Botryosphaeriaceae family and is involved in grapevine wood decay diseases. The present study reports the discovery and the molecular characterization of a novel mitovirus infecting this fungus. Double-stranded RNAs were purified from cultivated N. luteum and analysed by next generation sequencing. Using contigs showing BlastX homology with the RNA-dependent RNA polymerase (RdRp) gene of various members of the family Narnaviridae, a single contig of approximately 1.2 kb was constructed. The genomic sequence was completed and phylogenetic analyses indicated that this virus represents a new member of the genus Mitovirus, for which the name of "Neofusicoccum luteum mitovirus 1" is proposed. The genome is 2,389 nucleotides long and, based on the fungal mitochondrial genetic code, it encodes a putative protein of 710 amino acids, homologous to the RdRps of members of the Narnaviridae family. The neofusicoccum luteus mitovirus 1 (NLMV1) RdRp contains the six conserved motifs previously reported for mitoviral RdRps. Our findings represent the first evidence that a mycovirus can infect N. luteum, an important pathogenic fungus of grapevine.