The phenolic compounds in mortiño (Vaccinium floribundum Kunth, family Ericaceae) from the páramos of Ecuador were studied by LC-DAD−MS/MS for the first time. (−)-Epicatechin, one dimer A and one trimer A were found at a total concentration of 18 mg/100 g FW. Of the flavonol glycosides (38 mg/100 g FW), quercetin and myricetin were found as -3-O-hexosides, -3-O-pentosides and -3-O-deoxyhexosides. Chlorogenic and neochlorogenic acids together with caffeic/ferulic acid derivatives were found as predominant components among the hydroxycinnamic acids in the berry. Anthocyanins, including cyanidin and delphinidin derivatives, were the major phenolic compound class quantified (345 mg cyanidin-3-O-glucoside/100 g FW).