This study examines the enhancing effect of peer annotation on the academic English reading of nonnative-Englishspeaking graduate students. To facilitate peer collaboration, the present study included the development of a strategybased online reading system. Through peer annotation, the students not only achieved enhanced reading comprehension but also gained an awareness of various effective reading strategies. Using what the authors have named a "mobile annotation sharing system," a group of Taiwanese graduate students collaboratively read and annotated English papers. Afterward, surveys and interviews were conducted to determine participants' self-perceived degree of reading comprehension, the reading strategies they implemented, and their attitudes toward collaborative reading. The findings revealed that the participants appreciated the collaborative medium and the tasks associated with it. Access to their peers' annotations and the existence of a mutually supportive environment aided their reading comprehension and lowered their negative emotions. The implications for future implementation of collaborative online reading systems targeting English for academic purposes are discussed.