Theoretical values of ultrasonic velocity in the ternary mixtures of diisopropylether+2,2,2-trifluoroethanol+1-propanol have been evaluated at temperatures 303 K, 308 K and 313 K using Nomoto's Relation (U NR ), Junjie's Method (U JM ), Ideal Mixing Relation (U IMR ), Free Length Theory (U FLT ), Collision Factor Theory (U CFT ) and Impedance Dependence Relation (U IDR ). Theoretical values were compared with the experimental values and the validity of the theories was checked by calculating the average percentage error (APE).