© 2016 Elsevier B.V. In this work, Mo-doped SnO 2 nanoparticulate sensing films were fabricated by flame spray pyrolysis (FSP) and spin-coating processes with varying Mo-doping concentrations (0–2 wt%) and numbers of spin-coating cycles (1–5). Structural characterizations by electron microscopy and X-ray analysis suggested that Mo atoms were substitutionally doped in polycrystalline SnO 2 nanoparticles at low Mo concentrations ( < 1 wt%) but then segregated as secondary MoO 3 crystallites at high Mo levels (1–2 wt%). In addition, the incorporation of Mo resulted in the reduction of size and the increase of surface area of SnO 2 nanoparticles. The gas-sensing properties of sensors were investigated towards H 2 S, NO 2 , NH 3 , H 2 and CO at the working temperature ranging from 150 °C to 350 °C. The results showed that the moderate Mo-doping level of 0.5 wt% and the high number of spin-coating cycles of 4 led to the optimal enhancement of H 2 S response. The optimal Mo concentration could be correlated to the highest doping level that did not induce secondary MoO 3 crystallites. In particular, the 0.5 wt% Mo-doped SnO 2 sensor prepared with 4 spin-coating cycles exhibited a high response of ∼105 and a short response time of ∼5 s–10 ppm H 2 S at an optimal working temperature of 250 °C. Furthermore, the optimal sensor displayed good H 2 S selectivity against NO 2 , NH 3 , H 2 and CO. Therefore, the flame-spray-made Mo-doped SnO 2 thick film sensor is a promising candidate for sensitive and selective detection of H 2 S at a threshold limit value (TLV) of lower than 10 ppm and may be useful for general industrial applications.