Kiwiberry (Actinidia arguta), originating from northeast Asia, is a new fruit product. Since 2018, fruits of kiwiberry showing brown spots were observed in orchards of Zhejiang Province, China. Disease symptoms started from the initial stage of fruit development. The brown spots on young fruits extended as the fruits developed. The fungus strain isolated from the affected fruits was preliminarily identified as Alternaria species according to morphological characteristics. Further molecular identification based on a multi-locus phylogenetic analysis comprised of partial sequences of internal transcribed spacer (ITS) rDNA region, endopolygalacturonase (endoPG) gene, major allergen (Alta1) gene, and 28S ribosomal RNA (LSU) gene verified that the fungus is Alternaria alternata. The pathogenicity of the isolated fungus was confirmed by artificial inoculation. The present identification constitutes the first report of A. alternata as the causal agent of brown spot on kiwiberry in China.