This study explored the relative effect of recasts on second language (L2) Korean learners' accuracy development of the object relative clauses (RCs) and the honorific subject-verb (S-V) agreement in Korean and its relationship with language analytic ability (LAA). Forty-five L2 Korean learners participated in the study and five Korean native speakers participated as their dyadic partners. The learners were assigned into the recast group (n = 27) and the control group (n = 18). The recast group received recasts to their errors of the target forms from an interlocutor, a native Korean speaker, during their engagement in four communicative activities, but no recasts were provided to the control group. Three language tests (i.e. a pretest, an immediate posttest, and a delayed posttest) to measure accuracy development and a LAA test were applied to both groups. The study found that recasts benefited L2 Korean learners' accuracy development of both forms, but their effects were not equal: recasts were more effective for the object RCs than the honorific S-V agreement. In addition, the results showed that LAA had a positive effect on the extent to which the learners benefited from recasts.