The effects of $Nb_2O_5$ and $MnO_2$ on the positive temperature coefficient of resistivity (PTCR) behavior of lead-free $Ba_{0.99}(Bi_{1/2}Na_{1/2})_{0.01}TiO_3$ (BaBiNT) ceramics were investigated in order to fabricate a PTC thermistor available at high temperature of > $120^{circ}C$. In particular, 0.05 mol% $Nb_2O_5$ added BaBiNT ceramic, which has significantly increased Curie temperature (Tc) of $160^{circ}C$, showed good PTCR behavior; low resistivity at room temperature $( ho_r)$ of $80.1{Omega}{cdot}cm$, a high $ ho_{max}/ ho_{min}$ ratio of $5.65{ imes}10^3$ and a large resistivity temperature factor (a) of 18.5%/$^{circ}C$. Furthermore, the improved $ ho_{max}/ ho_{min}$ of $6.48{ imes}10^4$ and a of 25.4%/$^{circ}C$ along with higher $T_c$ of $167^{circ}C$ despite slightly increased $ ho_r$ of $569{Omega}{cdot}cm$, could be obtained for the BaBiNT + 0.05 mol% $Nb_2O_5$ + 0.02 wt% $MnO_2$ ceramic cooled down at a rate of $200^{circ}C/h$.