The electrical conductivities of complex hydrides Li2(BH 4)(NH2) and Li4(BH4)(NH 2)3 consisting of (BH4)- and (NH2)- anions are investigated focusing on their low melting temperatures (365 K for Li2(BH4)(NH2) and 490K for Li4(BH4)(NH2)3). The two hydrides show lithium fast-ion conductivities of about 1 × 10 -4 S·cm-1 at room temperature. After melting, the total ion conductivities OfLi2(BH4)(NH2) and Li4 (BH 4)(NH2)3 reach 6 × 10-2 S·cm-1 (378 K) and 2 x 10-1 S·cm -1 (513 K), respectively. The crystal structure and local atomistic structures closely correlated with the lithium ion conduction before and after melting are also discussed. ©2011 The Japan Institute of Metals.