The effect of nanosized NbC precipitates on electrochemical corrosion behavior of high-strength low-alloy (HSLA) steels in 3.5%NaCl solution has been investigated by the means of precipitate modulation, microstructure observation, electrochemical and immersion tests. The results showed that NbC precipitates markedly enhance the corrosion resistance of the H-contained steel, and the mechanism is that the plentiful and highly dispersed nanosized NbC particles acting as massive and effective hydrogen traps play a decisive role in the resistance to hydrogen activated corrosion. Moreover, it is evident that the inhibiting effect is related with the amount, size and distribution of the precipitates, and the optimized microstructures and precipitated phases improve the mechanical properties and resistance to hydrogen activated corrosion of HSLA steel. •NbC precipitates enhance the corrosion resistance of H-contained HSLA steel.•The mechanism is nanosized NbC acting as H traps with high activation energy.•The amount, size and distribution of the precipitates are effective factors.