The present study aimed at investigating the impact of textual enhancement on the comprehension of transparent and opaque English idioms among Spanish lower-intermediate students studying English as a foreign language. Two short texts including visually enhanced idioms (i.e., they were underlined) were designed for the Experimental Group, and the Control Group received an unenhanced version of the texts. The results reveal that textual enhancement made transparent idioms salient enough for them to have an impact on comprehension; however, underlining had a poorer effect on comprehension as far as opaque idioms are concerned. In addition, we aimed at examining the effect of textual enhancement on the noticing of idioms. Findings show that it did not have a positive effect on recognition of idioms, since the Control Group outperformed the Experimental Group in the multiple-choice task.