In the AI era, it has become crucial to evaluate information found on the Internet critically. This research aimed to investigate the impact of a sourcing organizer on sixth graders' online multimodal and multiple document reading (MMDR) abilities, focusing on aspects such as source-content link and text integration in relation to reading on the Internet. Cognitive and affective factors associated with MMDR were examined. The study involved 52 sixth-graders (55.77% males) from two typical elementary school classes in the northern region of Taiwan. Two intact classes were randomly assigned to either the experimental or control group with the quasi-experimental design. The experimental group (n = 26) received a pre-outlined sourcing organizer, guiding them to record the article title, author, publication date, website name, and major assertions from six assigned multimodal texts. In contrast, the control group (n = 26) received a regular organizer, prompting them to summarize the main ideas from the same six assigned multimodal texts. The study's findings indicated that employing sourcing organizers positively impacted students' performance in text integration. However, it was observed that both groups, regardless of whether they used regular organizers or sourcing organizers, experienced benefits in terms of source-content links. Furthermore, reading ability emerged as the sole significant predictor for source-content links, whereas both reading ability and the use of sourcing organizers predicted text integration. The implications of these findings were discussed to provide insights into instructional strategies to develop online MMDR competencies in elementary students.