With the development of PeerMark functions, Turnitin begins to capture researchers’ and instructors’ attention as a novel peer review tool. This article reports an empirical study that examines students’ peer feedback using Turnitin and their perceptions in two First-Year Writing classes, one for mainstream students and the other for ESL students. The participants conducted peer review activities using multiple Turnitin features (e.g., Commenting tools, Composition marks, and PeerMark questions) for two writing assignments–summary & response paper and argumentative paper. Analyses of archived Turnitin peer review records revealed that students provided a majority of revision-oriented feedback, in both global areas (e.g., content, organization, and citation) and local areas (e.g., vocabulary, grammar, mechanics, and format), although variations were identified across both classes and both tasks. Questionnaire survey and interviews indicated that students unanimously reported positive perceptions of Turnitin-based peer feedback. They appreciated distinctive features of Turnitin that facilitated their peer review activities; they also shared the perceived constraints and constructive suggestions. This study further informs affordances of new technologies for online peer review.