This study investigated the genetic variability of astroviruses in children with acute gastroenteritis in Japan in 2012 to 2013. A total of 330 fecal specimens collected from children with diarrhea were tested for astroviruses using RT-PCR and nucleotide sequencing techniques. Among the tested specimens, 54 (16.4%) were positive for astrovirus. Three different phylogenetic clades were detected. MLB was the most predominant clade (35 samples), followed by classic astrovirus (17 samples), and VA astrovirus (2 samples). Two types of MLB were identified (MLB1 and MLB2), while classic astroviruses were HAstV1 and HAstV4. Two VA astroviruses were identified as VA2. J. Med. Virol. 88:356–360, 2016. © 2015 Wiley Periodicals, Inc.