This longitudinal randomized trial study investigated the effects of phonological specificity training on second language (L2) vocabulary learning. Eighty-six Dutch secondary-school students participated in one of two experimental conditions or in an animacy judgment (active control) condition. Participants in the phonological specificity training (with phonological manipulation) and the picture selection (without phonological manipulation) experimental conditions had to select the corresponding picture from among competitors after hearing a word. Phonological specificity training resulted in increased learning (measured through word translation) compared to the control condition on the posttest whereas picture selection produced increased learning only for participants with larger initial vocabulary sizes. Both experimental conditions showed increased learning for participants with larger vocabulary sizes on the retention test. Compared to picture selection, phonological specificity training showed more learning immediately after intervention for words with nonnative contrasts. Results suggest that phonological features can augment (meaning-focused) L2 vocabulary learning interventions.