The methanolic extract of Xylia xylocarpa (Roxb.) Taub. (Mimosaceae) raw seed materials contained total free phenolic content of 14.35 ± 1.66 g catechin equivalent/100 g extract dry matter. Encouraging levels of ferric reducing/antioxidant power (1,096 mmol Fe[II]/mg extract), inhibition of β-carotene degradation (59.85%) and scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (72.31%) and superoxide (60.31%) radicals were exhibited by the methanolic extract of raw samples. Furthermore, it also recorded 82.23% of α-amylase and 77.28% of α-glucosidase enzyme inhibition characteristics under in vitro starch digestion bioassay. Sprouting + oil frying caused a significant increase in the total free phenolic content and also apparent improvement on the antioxidant and free radical-scavenging activities of X. xylocarpa seeds, while soaking + cooking as well as open-pan roasting treatments showed diminishing effects.