Developing excellent electrocatalysts is a significant step in accelerating the widespread implementation of the electrochemical hydrogen evolution reaction (HER). MoS2 is one of the promising alternatives to platinum-based catalysts, while its HER activity is far from Pt due to the lack of active sites. It is urgent to develop a novel strategy to activate the basal planes of MoS2 for enhancing the HER activity. Herein, a facile hydrothermal method with a low-temperature H2O2 etching method is developed to fabricate MoS2 with O-doped and S-vacancy dual defects. The dual defects MoS2 nanosheet demonstrates remarkable hydrogen evolution reaction (HER) activity, achieving 10 mA cm−2 with a small overpotential of around 143 mV in 0.5 M H2SO4.Graphical Abstract: Construct dual-defect MoS2 via a facile hydrothermal method and mild H2O2 etching process.