We explore the effect of Mo doping over the large enhancement of electrochemical property of Mo-doped SnO2 quantum dots (3–5 nm) grown over rGO (reduced graphene oxide) sheets by a soft chemical process in ambient conditions. The composites were prepared over a range of Mo doping concentrations (0–10%) and 5% Mo doping had achieved the best energy storage characteristics. The capacity of the active material could reach ∼851 mAh g−1 (@ 78 mA g−1) in the beginning and that retained ∼89% (∼758 mAh g−1) with superior cyclic stability (100 cycles) and rate capability (506 mAh g−1 @ ∼1.5 A g−1). The addition of the reductant of 0.06 mol during the synthesis procedure led to further improvement of the capacity to ∼875 mAh g−1 (∼92% retention) and the rate capability (∼587 mAh g−1). These impressive results are ascribed to the distribution of Mo-doped SnO2 QDs, doping of Mo6+ at Sn4+ lattice sites providing more electrons for easy electrical transport, reduction of GO (graphene oxide) to rGO. Mo doping led to the decline in the charge transfer resistance (Rct) from 14.99 Ω for un-doped SnO2/rGO to 14.09 Ω (2.5%), 11.61 Ω (5%), and 11.4 Ω (10%) and promote the electrochemical property of the composite. A simple room-temperature synthesis process was used to produce Mo-doped SnO2/rGO nanocomposite and can be employed for the production of many other oxides and their composites for interesting applications.