We investigated indexical variation as a variable that promotes second language (L2) vocabulary learning across language modalities. In three experiments, we presented Catalan Sign Language signs (Experiments 1a and 1b), pseudowords (Experiment 2), and English words (Experiment 3) to participants in three conditions that varied in the number of people who introduced these stimuli (one, three, or six people). We evaluated learning outcomes in two recall tasks: a picture-to-L2 naming task and a L2-to-L1 translation task. For the sign modality, indexical variation benefitted the immediate recall of signs in the translation task (Experiment 1a) and delayed recall after two weeks in the picture naming task (Experiment 1b). For the oral modality, we observed no effect when participants learned pseudowords (Experiment 2), but variability benefited recall in the translation task when participants learned English words (Experiment 3). We discuss these contrastive results, considering the influence of indexical variation in adult L2 sign and oral vocabulary learning.