This study utilized the ultrasound-assisted extraction method to obtain an extract rich in phenolic compounds from the leaves of Tricosanthes cucumerina. The optimization of the experimental design identified the optimal extraction conditions: a temperature of 40 °C, a duration of 6.25 min, and an amplitude of 40%. Under these conditions, the extraction yielded the highest levels of phenolic compounds, measuring 262.54 mg of GAE (gallic acid equivalent) per gram. Further analysis of these extracts using electrospray ionization mass spectrometry (ESI-MS) demonstrated that ultrasound extraction increased the availability of bioactive compounds, such as p-coumaric acid, ferulic acid, and caffeic acid. The resulting extract was microencapsulated with sodium alginate as the wall material and then lyophilized to enhance the shelf life and stability of the phenolic compounds. The thermogravimetric analysis confirmed that the microcapsules exhibited thermal stability, retaining their properties at temperatures up to 250 °C. Additionally, Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses corroborated the effectiveness of the encapsulation process. Consequently, the ultrasound-assisted extraction of T. cucumerina leaves is a promising alternative for incorporating bioactive compounds into food products, nutraceuticals, and cosmetics, thus benefiting consumers.