This study investigated the impacts of peer and teacher support on perceived technology usefulness and ease of use, and acceptance of computer-mediated collaboration in writing (CMCW) among Hong Kong primary school students, who learn English as a second/foreign language (ESL/EFL). The results showed that class-level peer support had direct and positive impacts on individual-level acceptance of CMCW. However, teacher support did not have direct impacts. Peer support had indirect impacts on acceptance of CMCW through perceived usefulness. Teacher support had indirect impacts on acceptance of CMCW through the mediation of perceived usefulness and ease of use. The findings highlight the importance of teacher and peer support in students' perceptions towards technology use and acceptance of CMCW. Reasons for the findings and implications for promoting CMCW are discussed.