Background: Peer-to-peer feedback exchanges have been recognized as crucial to language learning. While studies on peer feedback proliferate, little is known about whether and how peer feedback is affected by learners' motivational levels. Objectives: Situated in a mobile collaborative learning context, the current study examined how English as a Foreign Language (EFL) students with different motivational levels participated in mobile-assisted peer feedback provision, as well as the characteristics of the feedback they provided. Methods: A total of 61 sophomores majoring in Business English at a Chinese university participated in this 16-week-long study. They were asked to complete oral assignments and give and receive peer feedback via MosoTeach (a popular mobile learning application in China). Multiple types of data (peer feedback records, questionnaires, reflective journals and interviews) were collected, analysed, and triangulated. Results and Conclusions: Results revealed that EFL learners with higher motivation were more likely to provide feedback on time using more words. Unique characteristics of mobile-assisted peer feedback among highly motivated learners were also observed. Implications: The study highlights the importance of learner motivation in mobile-assisted peer feedback practice and provides pedagogical suggestions for better designing and implementing peer feedback in mobile collaborative learning contexts.