SnO₂ nanofibers with and without block copolymer P123 (EO₂₀PO₇₀EO₂₀) in the precursor are synthesized via a simple electrospinning method. The Brunauer–Emmett–Teller surface areas of the nanofibers with and without P123 are 113.261 and 18.025 m² g⁻¹, respectively. Gas sensing properties of these two samples are investigated by exposing the corresponding sensors to NH₃, C₂H₅OH, and CH₃COCH₃ at 280, 300, and 340 °C, respectively. Comparing with nanofibers without P123, the SnO₂ nanofibers with P123 hold enhanced response value, higher saturated-detection-concentration, and lower minimum-detection-limit. The response is 59, 75, and 65 for nanofibers with P123 to 500 ppm NH₃, C₂H₅OH, and CH₃COCH₃, respectively, and is 28, 50, and 43 for nanofibers without P123. The minimum-detection-limit is 5, 1, and 1 ppm for nanofibers with P123 to detect NH₃, C₂H₅OH, and CH₃COCH₃, respectively, and is 50, 20, and 10 ppm for nanofibers without P123. The improved gas sensing properties are based on their coarse and loose morphology and higher Brunauer–Emmett–Teller surface area brought by adding P123.