© 2017 Taylor & Francis Group, LLC. We studied the effects of BaTiO 3 (BT) seed nano-crystals on dielectric properties and phase transition behavior of Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 (BNKT) ceramics. The BaTiO 3 seed nano-crystals were used as nuclei, which acted as templates for starting materials to form perovskite phase. In this study, the BT seed nano-crystals were prepared by the molten salt technique. Eutectic mixtures of NaCl-KCl (1:1 by mole) were used as the flux. Various concentrations of BT seed nano-crystals were mixed with other precursors required for formation of BNKT phase, which was prepared by the solid-state method. Addition of BT seed nano-crystals enhanced the electrical properties of ceramics. The sample with 8 mol% BT seed nano- crystals exhibited highest value of dielectric constant (ϵ r ) at maximum temperature of 6700. The grain size significantly decreased with increasing concentration of BT seed nano-crystals. The relaxor ferroelectric behavior was also observed with the diffuseness parameter (γ) value being close to 2.