Elaeocarpus serratus L. leaves contain significant polyphenols, flavonoids, and myricitrin with medicinal property, which are byproducts after harvest and can be recovered for potential food applications. In this study, the effective extraction method for bioactive compounds and myricitrin from Elaeocarpus serratus L. leaves was investigated by comparing ultrasound-assisted extraction (UAE) and shaking-assisted extraction (SAE) for total phenolic content (TPC), total flavonoid content (TFC), myricitrin, and antioxidant capacity (as ferric reducing antioxidant power, FRAP). A first-order kinetic model of extraction was also proposed to correlate the observed extraction rate coefficient and limiting concentration of myricitrin in various solvents. Using defatted leaves (DL) as the substrate at the UAE condition of 95% ethanol with 1/10 (g/mL) of DL to solvent ratio under 40 kHz/300 W of ultrasound, 26.63% of yield of extract, and 199.75 mg-ferrous-sulfate-heptahydrate-equivalent/g-DL of FRAP were obtained. Further, the bioactive compounds extracted were 92.35 mg-gallic-acid-equivalent/g-DL of TPC, 53.14 mg-rutin-equivalent/g-DL of TFC, and 4.41 mg/g-DL of myricitrin, which were 1.53, 1.44, and 1.4 folds using SAE at 120 rpm, respectively. This showed that UAE was more efficient than SAE in bioactive compounds recovery for valorization of Elaeocarpus serratus L. leaves.