Idiomatic expressions pose substantial learning difficulties for learners across languages and tend to be acquired later in the course of language development both in L1 and L2. A number of factors have been identified as contributing to this difficulty. However, cross-linguistic studies on figurative language acquisition are still rare. The present study investigated the effect of semantic opacity and syntactic symmetry during the learning of Chinese four-character idioms (or QIEs: "quadra-syllabic idiomatic expressions") with 11-year-olds and adult native speakers. Participants first completed a sentence production task and then a multiple choice comprehension test. Results showed that the degree of semantic opacity consistently influenced participants' performance in both tasks; syntactic symmetry played a significant role in the comprehension but not in the sentence production task. Participants were better at understanding than producing sentences with QIEs. But few could form correct sentences with the QIEs that they did not comprehend correctly. The results are discussed in light of Nippold's metasemantic hypothesis and the salient linguistic feature of QIEs.