We studied mutual influences between native and non-native vowel production during learning, i.e., before and after short-term visual articulatory feedback training with non-native sounds. Monolingual French speakers were trained to produce two non-native vowels: the Danish /ɔ/, which is similar to the French /o/, and the Russian /ɨ/, which is dissimilar from French vowels. We examined relationships between the production of French and non-native vowels before training, and the effects of training with non-native vowels on the production of French ones. We assessed for each participant the acoustic position and compactness of the trained vowels, and of the French /o/, /ø/, /y/ and /i/ vowels, which are acoustically closest to the trained vowels. Before training, the compactness of the French vowels was positively related to the accuracy and compactness in the production of non-native vowels. After training, French speakers’ accuracy and stability in the production of the two trained vowels improved on average by 19% and 37.5%, respectively. Interestingly, the production of native vowels was also affected by this learning process, with a drift towards non-native vowels. The amount of phonetic drift appears to depend on the degree of similarity between the native and non-native sounds.