Display omitted •This work produces porous and ultralong Pt-In2O3 porous nanofibers using electrospinning and chemical soaking firstly.•The well-distributed Pt NPs can maintain the ultrasmall size in the surface of In2O3 PNTs without any protection.•The Pt-In2O3 PNTs sensor shows excellent acetone sensing properties compared to the pristine In2O3 PNTs.•The as-prepared sensor exhibits excellent gas sensing properties than other sensors based on In2O3 in previous reports. Here, we demonstrate a facile design and simple fabrication of acetone gas sensors based on one-dimensional (1D) porous platinum (Pt)-doped In2O3 nanofiber structure. Be first to try to immerse electrospun polystyrene (PS) nanofibers (NFs) into a precursor solution followed by an annealing process, the as-prepared composite NFs can readily turn into Pt-In2O3 porous NFs. The obtained Pt-In2O3 porous NFs exhibit the mesoporous size of 4–6 nm and high specific surface area of 212.3 m2 g-1. We observed that the spillover effect of Pt nanoparticles and the large-surface-area of the porous structure can effectively enhance catalytic sensing response to acetone with a lower limit of 10 part-per-billion (ppb) at a low working temperature of 180 °C. More importantly, the proposed NFs-based sensor shows rapid response and recovery time (6/9 s), higher selectivity toward acetone against other interfering gases, reversibility and time stability (50 days) compared to its counterparts. In addition, the proposed sensor shows a fast response and recovery time, maintaining 70% of the initial response even in 85% relative humidity (RH) environment. These results demonstrate the potential feasibility that the Pt-In2O3 porous NFs act as a promising sensing platform for monitoring acetone at ppb levels in human breath.