Abstract Air oxidation behaviour of a Ti–6Al–4V alloy was examined over the temperature range of 600–800 °C for different time intervals ranging between 0.5 and 72 h. In addition to the determination of the oxidation kinetics by weight gain measurements, oxygen diffusion zone (ODZ) depth and hardness measurements were conducted on the cross-sections of the oxidised alloys to investigate the diffusion kinetics of oxygen into the substrate. The rate of oxidation evaluated according to the weight gain measurements fitted parabolic kinetics between 600 and 700 °C and linear kinetics above 700 °C by yielding activation energies of 276 and 191 kJ/mol, respectively. Analysis of the ODZ depth and hardness measurements resulted in an activation energy of 202 kJ/mol for oxygen diffusion in Ti–6Al–4V alloy. Finally, the kinetics of oxidation and oxygen diffusion were evaluated by the analysis of the experimental data with respect to temperature-compensated time parameter.