<p>The addition of Cr and Ti elements gives V-4Cr-4Ti a ductile-to-brittle transition temperature as low as −140 ºC, significantly lower than that of pure V. However, the effect of oxygen solute on the deformability of V-4Cr-4Ti remains largely unexplored. Here, it is demonstrated that V-4Cr-4Ti exhibits significantly faster oxygen absorption kinetics compared to pure V. Although alloying with Ti can trap some oxygen solute, the remaining oxygen solute in the matrix severely embrittles the alloy. Profuse dislocation multiplication through kink formation and frequent cross-slips endows V-4Cr-4Ti with excellent low-temperature deformability. In contrast, oxygen-charged V-4Cr-4Ti containing 0.57 wt.% O shows severe embrittlement even at temperatures exceeding 200 ºC. High concentrations of oxygen solute, combined with Ti and Cr alloying elements, hinder dislocation motion, promote strain localization, and generate numerous super-jogs (sessile structures) and dislocation loops, collectively leading to embrittlement. These findings provide insights into the microscopic oxygen embrittlement mechanisms in V-4Cr-4Ti.</p> Graphical abstract <p></p>