We investigated the effects of metalinguistic awareness and the internal structure of Chinese characters on children's incidental learning of word meanings while reading. The participants were 241 Taiwanese children from six fourth-grade classes. They were randomly assigned to read one of two texts, and then their knowledge of unfamiliar characters from both texts was assessed. Two kinds of factors that might influence incidental learning of character meanings were examined: features of the unfamiliar characters (radical helpfulness, phonetic regularity, and contextual support) and child characteristics (radical awareness, phonetic awareness, general vocabulary, and prior knowledge of target characters). Results showed that children could incidentally learn characters during normal reading. Children who had more radical or phonetic awareness knew more characters, especially when the character contained a radical that gave a clue to meaning. However, contrary to expectation, radical helpfulness and phonetic regularity did not contribute to character learning. Characters were easier to learn when contextual support was strong.