The chemical lithiation of Aurivillius-type layered perovskite oxide, Bi4Ti3O12 (BTO), was demonstrated for the first time. The crystal and electronic structures of the lithiated BTO were characterized by neutron diffaction and X-ray absorption spectroscopic analyses. According to the neutron diffaction studies, it has been found that the lithium atoms are positioned between a perovskite block and a Bi2O2 layer. From the Bi L-III- and Ti K-edge XANES/EXAFS analyses, it has been found that significant amounts of Bi and Ti cations are reduced due to the Li-intercalation, and that the local structure around Ti becomes more distorted.