Academic English skills have been challenging for many students in English-medium universities in Hong Kong. Thus, the high demand for writing assistance has made peer tutoring an essential alternative to make up for the inadequate teaching resources. Extensive research on the language use (using both first language L1 and second language L2) in peer tutoring has laid a solid foundation in improving English writing and communication skills, yet limited empirical studies are available to examine the effects of peer tutoring in an English-medium (L2 only) context. The present study analyzes the effects of a writing consultation project to complement the existing English writing support services offered on English-medium university campuses. The study employs a triangulated approach in which a 360-degree monitoring and evaluation mechanism was set up to regulate the progress and effectiveness of the project at different implementation stages. Findings demonstrate that peer tutors play a key intermediary role between tutees and course teachers, suggesting that the project not only met the writing needs of non-native English-speaking students, but also fostered tutors’ whole personal growth and enhanced the meaningful use of their linguistic knowledge.