This study explores Chinese English-major students' intertextual competence and factors shaping their ability to paraphrase in academic writing. Multiple instruments were employed to collect data from 212 English-major students at different academic levels from nine universities in mainland China. The data were analyzed to determine how a range of personal and contextual variables related to their ability to paraphrase an academic text. Two groups of variables were found to be associated with their performance on the paraphrasing task. The first group comprised knowledge and attitudinal variables, including previous training on plagiarism, knowledge of blatant plagiarism, inability to recognize plagiarized texts, and condemnatory attitudes toward plagiarism. The second group consisted of ability measures or their proxy variables, namely English proficiency, instructional context and inadequate academic ability as a perceived cause of plagiarism. The observed relationship between the two groups of variables indicated that the effects of knowledge and attitudinal variables depended on or were mediated by the ability variables. These findings call for a multipronged and coordinated pedagogical approach to developing students' intertextual competence.