The phytochemical investigation on the bark of Cryptocarya griffithiana Wight. (syn. Cryptocarya infectoria Miq.) resulted in the isolation and identification of six isoquinoline-derived alkaloids known as (+)-N-methyl-isococlaurine (1), (+)-reticuline (2), (+)-laurotetanine (3), (+)-N-methyllaurotetanine (4), atherosperminine (5), and argentinine (6), while the leaf extract yielded two alkaloids namely argentinine (6) and liriodenine (7). The structures were elucidated by extensive analyses of 1D and 2D NMR (COSY, HSQC, and HMBC) spectroscopy in combination with MS, and literature values. The alkaloids 2, 3, 6, and 7 are reported for the first time from this species and are regarded as significant for the genus Cryptocarya. Furthermore, this is the first report on the isolation of 6 and 7 from the genus Cryptocarya, which indicates that C. griffithiana holds considerable chemo-taxonomic importance within the genus. Our findings showed that this plant is rich in isoquinoline alkaloids and possessed a strong relationship with other Cryptocarya species.