Acetone detection at the parts-per-billion (ppb) level is achieved in this work using selective and optimized Fe doping of the three-dimensional (3D) flower-like SnO2 hierarchical microstructures. These structures were successfully synthesized via a one-step hydrothermal route. Detailed information about the crystal structure, surface morphology and composition of the Fe-doped SnO2 microstructures was investigated using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. Gas sensing experiments were conducted on the as-prepared Fe-doped SnO2 sensors. The measured results show that the incorporation of Fe into the SnO2 structure can greatly enhance the gas sensing properties of SnO2 sensors under the optimum working temperature (200 degrees C). Specifically, the 1.0 mol% Fe-doped SnO2 microstructures exhibit the highest response, fast response/recovery time, lowest detection limit and good selectivity and long-term stability. The results demonstrate that the developed Fe-doped SnO2 gas sensor has great potential for ppb-level acetone detection in many practical applications.