We report here the excess molar volumes and viscosities of di-n-butyl ether + 1-propanol + n-decane mixtures and their corresponding binary mixtures, di-n-butyl ether + n-decane and l-propanol + n-decane, at the temperature of 308.15 K under atmospheric pressure. This communication forms part of our studies on viscosities, excess molar volumes and excess molar enthalpies of binary and ternary mixtures containing di-n-butyl ether, I-alkanol, and alkanes at several temperatures and normal atmospheric pressure. Densities and kinematic viscosities were measured using an Anton Paar DMA 60/602 vibrating tube densimeter and an automatic Schott-Gerate viscometer. The experimental viscosities were used to test different semiempirical relations. The measured ternary data were also compared with empirical expressions for estimating ternary properties from binary data.