Total phenol content determined by the Folin-Ciocalteu assay and total antioxidant capacity measured by the ABTŠ•+ method were applied for the first time to analyze the aqueous extract prepared from the dried aerial parts of Mentha cervina, a Portuguese mint species traditionally used as a culinary herb in river fish-based dishes and currently commercialized to prepare digestive infusions. LC-MS/MS analysis was performed directly on the crude aqueous extract allowing the identification of seven phenolic compounds. The overall plant aroma was analyzed by the SPME/GC-MS method; this approach allowed the characterization of various constituents, as well as the comparison between the fresh and dried plant material. Such a comparison highlighted several metabolic changes that occur during the drying process of the aerial parts of this plant.