A rare rotavirus, RVA/Human-wt/KOR/CAU12-2/2012/G11P[25], was isolated from a 16-year-old female with fever and diarrhea during the 2012 rotavirus surveillance in South Korea using a cell culture system, and its full genome sequence was determined and analyzed. Strain CAU12-2 exhibited a G11-P[25]-I12-R1-C1-M1-A1-N1-T1-E1-H1 genotype constellation. Phylogenetic analysis of this strain revealed that it is a human-porcine reassortant of two distant relatives of the G11 strains circulating in the world. The VP7 and VP4 genes are most closely related to those of human G11P[25] viruses (Dhaka6, KTM368, and N-38 strains) identified in South Asia, whereas the VP1 gene originated from a porcine G11P[7] virus (YM strain) that was identified in South America. The VP6 gene was found to belong to the new genotype I12. This study indicates that the G11-P[25]-I12 genotype was introduced into the South Korean population by interspecies transmissions of human and animal rotaviruses, followed by multiple reassortment events.