An investigation of microstructural development in transient liquid phase bonds between the B2 type intermetallic compound NiAl and a nickel-base superalloy MM-247 is presented in this paper. The bonds discussed in the paper employed pure copper interlayers. Based on edge-on transmission electron microscopy investigations, the paper examines both microstructural development at the bond-line and the influence of bonding on the adjacent substrates. The paper considers the epitaxial growth of the B2 type beta (nominally NiAl) phase into the joint and the formation of non-epitaxial beta-phase layers. The paper also examines the formation of second-phases, including the L1(2) type gamma＇-phase (nominally Ni-3(Al, Ti)), MX type carbides, sigma-phase intermetallics and elemental chromium and tungsten. Bond-line and adjacent substrate microstructures for the NiAl/Cu/MM-247 bonds are correlated with joint mechanical properties determined by room-temperature shear testing. The paper compares the microstructure and mechanical properties of NiAl/Cu/MM-247 bonds with those of NiAl/Cu/Ni joints.