Recent works showed that elicitation, supported by precursor feeding, could be a strategy to increase phenolic content. However, these studies have never been conducted in viticulture. This strategy could be of greater interest in Garnacha, a grape variety characterized by its low phenolic content. Therefore, this work studied elicitation with methyl jasmonate (MeJ), supported by precursor feeding with phenylalanine (Phe), in order to improve Garnacha grape phenolic content. Results showed that Phe+MeJ treatment did not improve phenolic content to a greater extent than the corresponding individual treatments. Overall, the greatest improvement was obtained with MeJ application, followed by Phe+MeJ; while Phe treatment barely increased phenolic compounds. Consequently, it was not possible to confirm the hypothesis that elicitation by MeJ could be supported by precursor feeding with Phe, when both applied together. This is the first study dealing with this matter under field conditions serving as basis for future works.