Positive temperature coefficient of resistivity (PTCR) characteristics of (1-x)BaTiO3-x(Bi0.5K0.5)TiO3ceramics doped with Nb2O5 were investigated in order to develop the Pb-free PTC thermistor available at hightemperatures of >120oC. The PTCR characteristics appearing in the (Bi0.5Ki0.5)TiO3 (<5mol%) incorporatedBaTiO3 ceramics, which might be mainly due to Bi+3 ions substituting for Ba+2 sites. The 0.99BaTiO3-0.01(Bi0.5K0.5)TiO3 ceramics showed good PTCR characteristics of a low resistivity at room temperature (ρr) of31 Ω·cm, a high ρmax/ρmin ratio of 5.38×103, and a high resistivity temperature factor (α) of 17.8%/oC. Theaddition of Nb2O5 to 0.99BaTiO3-0.01(Bi0.5K0.5)TiO3 ceramics further improved the PTCR characteristics.Especially, 0.025mol% Nb2O5 doped 0.99BaTiO3-0.01(Bi0.5K0.5)TiO3 ceramics exhibited a significantly increasedρmax/ρmin ratio of 8.7×103 and a high α of 18.6%/oC, along with a high Tc of 148oC despite a slightly increasedρr of 39 Ω·cm.