It is generally agreed that first language (L1) morphological awareness, the ability to reflect upon, analyze and manipulate morphemes and morphological structure of words, can transfer and facilitate second language (L2) reading subskill acquisition. However, the facilitative role of L1 morphological awareness is unclear in the literature investigating third language (L3) reading. This study explored if and how L1 morphological awareness and L2 reading subcomponent skills contribute jointly to L3 lexical inferencing in syllabic L1 Japanese-alphabetic L2 English-morphosyllabic L3 Chinese university learners. Sixty-seven students were recruited from novice-level, first-year Chinese classes from a Japanese university. Only 56 students completed 7 computerized or paper-and-pencil tasks, including L1 Japanese morphological awareness, L2 English morphological awareness, L2 English vocabulary knowledge, L2 English lexical inferencing, L3 Chinese morphological awareness, L3 Chinese vocabulary knowledge, and L3 Chinese lexical inferencing. They also completed a self-reported proficiency questionnaire survey. Correlational and regression analyses were conducted. The results suggested that there was only a significant association between L1 Japanese morphological awareness and L3 Chinese lexical inferencing, and there were no significant correlations between L2 English reading subcomponent skills and L3 Chinese lexical inferencing. Discussion is provided regarding the crosslinguistic influence of L1 morphological awareness in L3 reading development and the implications for L3 reading instruction.