Densities (ρ) and viscosities (η) of 1-methylimidazolium acetate ([Mim]Ac) protic ionic liquid+water mixture were measured at T=(293.15, 298.15, 303.15, 308.15 and 313.15) K under atmospheric pressure. Refractive indices (n D ) and electrical conductivities (κ) of the above-mentioned system over the entire composition range were measured at 298.15K. Excess molar volumes (V E ), viscosity deviations (Δη) and refractive index deviations (Δn D ) were obtained from the experimental data and fitted to the Redlich–Kister equation with satisfactory results. The results show that V E values of the system are negative over the whole composition range, whereas Δη and Δn D values are positive. Other volumetric properties such as apparent molar volumes (V ϕi ), partial molar volumes (V¯m,i) and excess partial molar volumes (V¯m,iE) of the system were calculated from the density data. The concentration dependence of κ was fitted according to the empirical Casteel–Amis equation. The measured and derived properties were employed to investigate the intermolecular interactions of the system.