Despite the growing interest in incorporating textual glosses into second language (L2) reading in hypermedia and paper media, no agreements have been reached as to whether and what extent a textual gloss facilitates L2 learners' vocabulary acquisition in hypermedia and paper media. The present study meta-analysed the overall effects of textual glosses and different glossing types (i.e. language, location, and mode) on L2 vocabulary acquisition, as well as the moderation effects on the variability of L2 vocabulary acquisition effect sizes. Based on a comprehensive search, 20 studies involving 2,291 participants that have quantitatively documented the changes of L2 vocabulary gains through a pre-and-post textual glosses design were identified and coded in order to retrieve moderator variables. The results show the following: (1) textual glossing has a medium effect on L2 vocabulary acquisition; (2) the effect of textual glosses on L2 vocabulary acquisition persists over time; (3) glossing location and glossing mode significantly impact the effect of textual glosses on L2 vocabulary acquisition but glossing language has no definite effect; and (4) outcome measure is the only moderator variable among the three influencing factors on vocabulary acquisition. These results are further discussed with reference to existing studies and theory of second language acquisition.