This study assesses the use of ultrasonication to improve the extraction process of classical solvent extraction methods for extracting isoflavones from the kudzu roots waste. The kudzu roots waste was produced after squeezing fresh kudzu roots to make juice. The effects of extraction time, extraction temperature, ultrasonic power, and ethanol concentration in ethanol/water mixtures were investigated. The extraction yield was found to increase with extraction time and temperature. The application of ultrasonication-assisted extraction (UAE) increased the extraction yield of water/ethanol mixture (20:80) at $25^{circ}C$ 3 fold. A maximum amount (7.28 g) of isoflavone was obtained from 100 g of dried kudzu roots waste by UAE with water/ ethanol mixture (20:80) for 6 h at $80^{circ}C$. Combining the use of ultrasonication with conventional vacuum evaporation method also reduced the concentration time for extracts from 45 to 24 min.