The ascomycete family Niessliaceae presently includes the genera Cryptoniesslia, Melanopsamma, Niesslia, Taiwanascus, Trichosphaerella, and Valetoniella. To this assemblage are added the newly described Circinoniesslia, with C. nectriae, and Valetoniellopsis, with V. laxa as their respective type species. The synonymy of Pseudorhynchia with Trichosphaeria is not accepted, and Pseudorhynchia is redescribed based on its type species. Melanopsamma pomiformis is redescribed and illustrated. Other newly described species are Melanopsamma verrucosa, Valetoniella pauciornata, and Valetoniella claviornata. The family Taiwanascaceae, described for the cleistothecial Taiwanascus tetrasporus, is placed in synonymy with the Niessliaceae. Trichosphaerella arecae is transferred to Neorehmia, and that genus is excluded from the family. Key words: Ascomycetes, Cryptoniesslia, Melanopsamma, Niesslia, Pseudorhynchia, systematics, Taiwanascus, Trichosphaerella, Valetoniella, Valetoniellopsis.