A capillary-microreactor assisted by ultrasound irradiation was designed and demonstrated to carry out aqueous-organic chemical reactions. The hydrolysis of benzyl chloride in a two-phase slug flow system was investigated. The capillary-microreactor was irradiated by 28 kHz ultrasound at different temperatures, capillary lengths and phase flow rates. It was found that the combination of microreactor technology and the ultrasound irradiation provides a promising protocol for process intensification. Under sonication conditions, higher mass transfer rates were obtained compared to silent conditions. The presence of ultrasound has affected the multiphase slug size and promoted better internal circulation within these slugs. Similar hydrodynamics behavior was noticed at higher temperatures for both sonication and silent conditions.