Herpotrichiellaceae is an interesting, but confused family in Chaetothyriales; the latter has been considered to represent a natural and well-defined group. A new genus Melanoctona was collected on decaying wood of Tectona grandis in Chiang Rai Province, Thailand and is introduced in Herpotrichiellaceae. It has a unique combination of morphological and phylogenetic characters. Phylogenetic analyses of combined ITS, LSU and SSU sequence data place Melanoctona in a distinct lineage in Herpotrichiellaceae. Melanoctona is distinguished from other genera in Herpotrichiellaceae by its hyphomycetous formation and muriform, ellipsoidal to ovoid, brown to dark brown conidia. Minimelanolocus yunnanensis sp. nov. is also introduced. This species inhabits decaying wood in freshwater streams and rivers in Yunnan Province, China. Maximum likelihood, maximum parsimony and Bayesian analyses of combined ITS, LSU and SSU sequence data, as well as a distinct morphology provide evidence for this new species. Comprehensive descriptions and illustrations of Melanoctona tectonae gen. et sp. nov. and Minimelanolocus yunnanensis sp. nov. are provided with notes on their taxonomy and phylogeny. Minimelanolocus yunnanensis is compared with morphologically similar taxa.