We conducted a systematic review of research involving K-12 students that examined associations among individual differences factors (e.g., working memory) and intertextual integration. We identified 25 studies published in 23 peer-reviewed journal articles and two dissertations/theses. These examined a wide range of individual difference factors, which we organized into four categories: (a) language and literacy, (b) cognition and metacognition, (c) knowledge and beliefs, and (d) motivation, emotion, and personality. We found large variation in the participants, tasks, and document types, and little systematic replication across studies. Nonetheless, results generally showed that variation in literacy, cognition, metacognition, knowledge, beliefs, and motivation are positively and moderately associated with intertextual integration. We discuss the limitations of this work and offer four recommendations for future research.