This study launched an investigation into the extent to which textual enhancement in captions can promote learner attention to and subsequent development in second language (L2) grammar. Using eye-tracking, it also intended to extend research on the relationship between attention and L2 learning. A pretest-posttest experimental design was employed, with 3 treatment sessions. Forty-eight Korean learners of L2 English were randomly assigned into a captions group (n = 24) and an enhanced captions group (n = 24). For the enhanced captions group, the components of pronominal anaphoric reference were boldfaced in the treatment task input. Learner attention to anaphora antecedents and personal pronouns was assessed with eye-movement indices, and a written and an oral grammaticality judgment test were used to measure learning gains. Textual enhancement succeeded in directing learner attention to the anaphora antecedents, and led to increased gains in receptive knowledge of pronominal anaphoric reference. However, significant links between attention and L2 development were only observed for the unenhanced captions group. The findings, overall, demonstrate that textually enhanced captioning is a useful pedagogical tool to facilitate development in L2 grammatical knowledge.