Previous evidence has suggested that acoustic similarity between first language (L1) and second language (L2) sounds is an accurate indicator of the speakers’ L2 classification patterns. This study investigates this assumption by examining how speakers of an under-researched language, namely Cypriot Greek, classify L2 English vowels in terms of their L1 categories. The experimental protocol relied on a perception and a production study. For the purpose of the production study, two linear discriminant analysis (LDA) models, one with both formants and duration (FD) and one with only formants (F) as input, were used to predict this classification; the models included data from both English and Cypriot Greek speakers. The perception study consisted of a classification task performed by adult Cypriot Greek advanced speakers of English who permanently resided in Cyprus. The results demonstrated that acoustic similarity was a relatively good predictor of speakers’ classification patterns as the majority of L2 vowels classified with the highest proportion were predicted with success by the LDA models. In addition, the F model was better than the FD model in predicting the full range of responses. This shows that duration features were less important than formant features for the prediction of L2 vowel classification.