Densities (rho) and viscosities (eta) for the ternary system of decalin (1) + methylcyclohexane (2) + cyclopentanol (3) and three corresponding binary systems have been measured over the whole composition range at 11 temperature points from 293.15 K to 343.15 K under atmospheric pressure (0.1 MPa). The excess molar volumes (V-m(E)) and viscosity deviations (Delta eta) of binary systems have been calculated and further fitted with the Redlich-Kister equation, while corresponding physical data of the ternary system have been correlated via the Clibuka, Singh, Nagata-Tamura, and Redlich-Kister equations. The V-m(E) values are negative for the binary system of decalin (1) + methylcyclohexane (2) with a minimum when the moles of the two components are similar. For the system of decalin (1) + cyclopentanol (2), the V-m(E) values are always positive with a maximun at about x(1) = 0.6. At the same time, a sigmoid curve can be observed for the system of methylcyclohexane (1) + cyclopentanol (2). The minimum and maximum appear around x(1) = 0.2 and x(1) = 0.9, respectively. The Delta eta values of the three binary systems are all negative and the absolute values decrease with increase in temperature. For the ternary system, the V-m(E) values are partially negative and the Delta eta values are negative over the entire concentration range. The nonideal behaviors of the mixtures are discussed in the perspective of intermolecular interaction and structural effect.