Duplex Stainless Steel (DSS) have two phase microstructures, mostly ferrite and austenite. They usually solidify as primary ferrite and part of which transforms into austenite on subsequent cooling. When ferrite and austenite are in near equal volume, DSS are quenched to retain this high temperature microstructure at room temperature. Holding these steels at single phase ferrite region for a long period will result in coarse grained structure which could impair the mechanical properties. In this study test coupons of DSS grade SAF 2205 were held at 1300°C for 15, 30, 60 and 90 minutes period and later water quenched. Microstructural investigations showed that dissolution of austenite was not completed even for 90 minutes holding at 1300°C, meaning that this temperature is below the solvus line. However, noticeable grain coarsening could be observed. Longitudinal velocities and attenuation co-efficient of ultrasonic waves produced with 5 MHz transducers were evaluated for these heat-treated coupons. Results show that the attenuation characteristics and longitudinal velocity ultrasonic waves are strongly influenced by the microstructural features. Attenuation increases with increase in grain size while longitudinal velocity is influenced by both the austenite content and the grain size.