Abstract: Alloying different semiconductors is a powerful approach to tuning the optical and electronic properties of semiconductor materials. In halide perovskites (ABX3), alloys with different anions have been widely studied, and great band gap tunability in the visible range has been achieved. However, perovskite alloys with different cations at the “B” site are less understood due to the synthetic challenges. Herein, we first have developed the synthesis of single-crystalline CsPbxSn1–xI3 nanowires (NWs). The electronic band gaps of CsPbxSn1–xI3 NWs can be tuned from 1.3 to 1.78 eV by varying the Pb/Sn ratio, which leads to the tunable photoluminescence (PL) in the near-infrared range. More importantly, we found that the electrical conductivity increases as more Sn2+ is alloyed with Pb2+, possibly due to the increase of charge carrier concentration when more Sn2+ is introduced. The wide tunability of the optical and electronic properties makes CsPbxSn1–xI3 alloy NWs promising candidates for future optoelectronic device applications.