English phraseology abounds with alliterative multiword units (e.g., slippery slope), which suggests that alliterative word strings have a comparative advantage to become stock phrases. One plausible explanation for this advantage is that alliterative word strings are relatively memorable, all else being equal, although there is little directly pertinent empirical evidence. In the context of instructed second language acquisition, it has been suggested that alliteration has a good potential to facilitate the learning of multiword units (MWU), at least when learners are made aware of the presence of alliteration in these units. In the present article, we investigate whether alliteration also makes MWUs comparatively memorable also "in the absence" of awareness-raising. English alliterative phrases and matched controls were dictated to EFL learners whose ability to recall the phrases was subsequently gauged in unannounced tests. We found a modest, short-lived mnemonic effect of alliteration. This points to an important role for awareness-raising if teachers or materials writers wish to help learners capitalise on the mnemonic advantage afforded by alliteration.