Mn modified 0.26Pb(In1/2Nb1/2)O3−0.42Pb(Mg1/3Nb2/3)O3−0.32PbTiO3 (PIN-PMN-PT:Mn) single crystals with orthorhombic perovskite crystal structure were polarized along [011] direction, resulting in the single domain state “1O.” The complete set of material constants was determined using the combined resonance and ultrasonic methods. The thickness shear piezoelectric coefficient d15 and electromechanical coupling factor k15 were found to be on the order of 3100 pC/N and 94%, respectively, much higher than longitudinal d33 ∼ 270 pC/N and k33 ∼ 70%. Using the single domain data, the rotated value of d33* along [001] direction was found to be 1230 pC/N, in agreement with the experimentally determined d33 value of 1370 pC/N, conferring extrinsic contributions being about 10%, which was also confirmed using the Rayleigh analysis. In addition, the mechanical quality factors Qm were evaluated for different “1O” vibration modes, where the longitudinal Qm was found to be ∼1200, much higher than the value for “4O” crystals, ∼300.