Purpose: The present study evaluated the applicability of the sentence-focused framework to Mandarin-speaking children with cochlear implants (CIs) by examining the relative contribution of receptive/expressive noun and verb lexicon sizes to later grammatical complexity. Method: Participants were 51 Mandarin-speaking children who received cochlear implantation before 30 months of age. At 12 months after CI activation, parents were asked to endorse words that their child could understand only or understand and say using the infant version of the Early Vocabulary Inventory. At 24 months after CI activation, parents were asked to endorse the grammatical structures that their children were able to say using the Grammatical Complexity subtest in the Mandarin Communicative Development Inventory--Taiwan. Children's receptive/expressive noun and verb lexicon sizes and grammatical complexity scores were computed from these parent checklists. Results: Correlational analyses showed that children's receptive/expressive noun and verb lexicon sizes at 12 months after CI activation were all highly correlated with their grammatical complexity scores at 24 months after CI activation ([rho]s = 0.52-0.63, ps < 0.001). Regression analyses further revealed that verb lexicon sizes at 12 months after CI activation outweighed noun lexicon sizes in accounting for grammatical complexity at 24 months after CI activation. Conclusions: Our findings supported the prediction of the sentence-focused framework. Emphasizing the role of verbs in early intervention has the potential to enhance grammatical outcomes in Mandarin-speaking children with CIs.