The $Bi_2O_3$ nanowires are highly sensitive to low concentrations of $NO_2$ in ambient air and are almost insensitive to most other common gases. However, it still remains a challenge to enhance their sensing performance and detection limit. This study examined the influence of the encapsulation of ${eta}-Bi_2O_3$ nanorods with $In_2O_3$ on the $NO_2$ gas sensing properties. ${eta}-Bi_2O_3-core/In_2O_3-shell$ nanorods were fabricated by a two-step process comprising the thermal evaporation of $Bi_2O_3$ powders and sputter-deposition of $In_2O_3$. Multiple networked ${eta}-Bi_2O_3-core/In_2O_3-shell$ nanorod sensors showed the responses of 12-156% at 1-5 ppm $NO_2$ at $300^{circ}C$. These response values were 1.3-2.7 times larger than those of bare ${eta}-Bi_2O_3$ nanorod sensors at 1-5 ppm $NO_2$. The enhancement in the response of ${eta}-Bi_2O_3$ nanorods to $NO_2$ gas by the encapsulation by $In_2O_3$ can be accounted for based on the space-charge model.