Scab (caused by Venturia carpophila) is a major disease affecting peach in the eastern U.S.A. The aims of the study were to characterize the mating type loci in V. carpophila, determine whether they are in equilibrium, and to assess the population genetic diversity and structure of the pathogen. The mating type gene MAT1-1-1 was identified in isolate JP3-5 in an available genome sequence, and the MAT1-2-1 gene was PCR amplified from isolate PS1-1, thus indicating a heterothallic structure. Mating type loci structure were consistent with those of other Venturia species (V. effusa and V. inaequalis): the mating type gene is positioned between APN2 encoding a DNA lyase and a gene encoding a Pleckstrin homology domain. Primers designed to each of the mating type genes and a reference gene TUB2 were used as a multiplex PCR reaction to screen a population (n = 81) of V. carpophila from various locations in the eastern U.S.A. Mating types in five of the nine populations studied were in equilibrium. Among the 81 isolates, there were 69 multilocus genotypes. A population genetic analysis of the populations with >10 individuals (four populations) showed them to be genetically diverse. Linkage disequilibrium was found in five of nine populations with ≥4 isolates. A discriminant analysis of principal components indicated three genetic clusters, although extensive admixture was observed. Mating type identification in V. carpophila provides a basis for understanding reproductive methods of the pathogen and can be a basis for further studies of genetics of the peach scab pathogen.