Phytochemical investigation of the bark of Guatteria friesiana afforded 12 new aporphines (<b>1b>–<b>12b>), along with nine known alkaloids (<b>13b>–<b>21b>). The structures of the new alkaloids were determined on the basis of spectroscopic data interpretation. The cytotoxic activity of the isolated compounds against a small panel of tumor cell lines was assessed using the Alamar blue assay.