Current methods used in the dairy industry to characterize the dissolution process are difficult to reproduce and subjective. Low-intensity ultrasound spectroscopy has the advantage of being rapid and precise, but the equipment is expensive. An ultrasonic flaw detector (UFD) is an economical alternative and allows for rapid data collection at a single frequency. This study focused on characterizing the dissolution behavior of whey protein concentrate (WPC) with an UFD. The experimental setup included an UFD (Epoch LTC) in pulse-echo mode and a 1MHz immersion transducer. Two batches of WPC80 from a commercial manufacturer were stored at 25°C and 40°C for 3 weeks. 19.74g of WPC was gradually added to 375g water. The tests were performed in duplicate. During dissolution, ultrasonic (US) data from UFD, chord length distribution from focused beam reflectance measurement (FBRM), and solubility index were collected at regular intervals for 1800s. US relative velocity and attenuation were calculated from A-scan data obtained from the UFD. The relative velocity was defined as the ratio of the US velocities of WPC solution and water at 40°C. It was observed that fresh WPC had a relative velocity of 1 after 1800s. The relative velocity at 1800s increased for powders stored at 25°C and decreased for powders stored at 40°C. After 3 weeks of storage at 25°C and 40°C, the relative velocities were 1.015 and 0.98, respectively. Attenuation had a general trend of increasing and then gradually decreasing. The storage temperature of WPC influenced the time to reach the peak and the area under the attenuation curve. Fresh powders reached the peak after 1440s. Three weeks of storage at 25°C and 40°C caused the peak time to increase to 1658s and decrease to 986s, respectively. The area had a similar trend. Fresh powders had an area of 60Np*s/m. Powders stored at 25°C and 40°C for 3 weeks had areas of 47Np*s/m and 91 Np*s/m, respectively. Storage temperature significantly (P < 0.05) effected relative velocity at 1800s, peak time, and area. FBRM data showed that powders stored at 40°C for 3 weeks had larger particles. Overall, a UFD can be a useful tool when characterizing the dissolution behavior of WPC.