A novel experimental method was developed through a ball-on-disk tribometer to study the friction and wear behaviour of a chrome steel at temperatures of 25, 200 and 500 °C. Water-based nanolubricants containing different concentrations of nano-TiO2 from 0.4 to 8.0 wt% were used to investigate their effects on friction-reduction and anti-wear mechanisms, in comparison to the benchmarks under dry and water conditions. The results show that the water-based nanolubricants can significantly reduce coefficient of friction (COF) and improve wear resistance of the chrome steel at both ambient and elevated temperatures. In particular, the use of nanolubricant containing an optimal concentration (4.0 wt%) of nano-TiO2 leads to the lowest COF and the smallest ball wear among all the lubrication conditions. The friction-reduction and anti-wear mechanisms are ascribed to the rolling & polishing effects, semisolid film and solid layer contributed by the nano-TiO2 at temperatures of 25, 200 and 500 °C, respectively.