Mytilinidioid fungi are conchiform in nature, with the appearance of bivalve shells or wedge-shaped, rigid, brittle, and carbonaceous hysterothecia growing on the bark of gymnosperms or angiosperms. Based on their morphological characteristics and molecular markers (ITS and LSU), this study describes three new species of mytilinidioid fungi: Ericboehmia mexicana of the family Hysteriaceae of the order Hysteriales and Lophium pinicola and Mytilinidion mexicanum of the family Mytilinidiaceae of the order Mytilinidiales. The first species grows on Liquidambar styracyphlua, the second species grows on Pinus patula, and the third species grows on Acacia californica subsp. pringlei. The specimens studied were deposited in the ENCB Herbarium.