We report the effect of Y substitution for Nb on Li ion conductivity in the well-known garnet-type Li5La3Nb2O12. Garnet-type Li5La3Nb2−x Y x O12−δ (0≤x≤1) was prepared by ceramic method using the high purity metal oxides and salts. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), 7Li nuclear magnetic resonance (Li NMR) and AC impedance spectroscopy were employed for characterization. PXRD showed formation of single-phase cubic garnet-like structure for x up to 0.25 and above x =0.25 showed impurity in addition to the garnet-type phases. The cubic lattice constant increases with increasing Y content up to x =0.25 in Li5La3Nb2− x Y x O12−δ and is consistent with expected ionic radius trend. 7Li MAS NMR showed single peak, which could be attributed to fast migration of ions between various sites in the garnet structure, close to chemical shift 0ppm with respect to solid LiCl and which confirmed that Li ions are distributed at an average octahedral coordination in Li5La3Nb2− x Y x O12− δ . Y-doped compounds showed comparable electrical conductivity to that of the parent compound Li5La3Nb2O12. The x =0.1 member of Li5La3Nb2− x Y x O12− δ showed total (bulk + grain-boundary) ionic conductivity of 1.44×10−5 Scm−1 at 23°C in air.