While numerous studies report the significance of social contexts in infant’s word learning, data concerning adults are scarce. This study aims to fill this gap. Specifically, it investigated the extent to which a number of the parameters associated with joint attention (e.g., direction and timing of eye-gaze between learners and target objects) help adults learn new words (i.e., map new objects with new labels). The study adopted a novel experimental paradigm where live interactions between two learners took place in four different learning contexts. An eye-tracker recorded learners’ eye-gaze during the experiment. Adult learners learned new words most successfully when they shared both the direction and timing of their eye-gaze towards the target objects. In addition, word learning initiated by a leaner alone, without sharing eye-gaze with another, failed to match these results. Overall, this study supports the view that joint attention maximizes adults’ learning of new words.