Technology-enhanced collaborative writing for second language learning has been receiving accumulating attention from researchers and educators over years. However, there was a lack of updated review with foci on the types and effectiveness of technologies in collaborative writing. This study conducted a systematic and in-depth review of 34 relevant empirical studies from 2009 to 2019. The results showed that wikis, Google Docs, offline word processors, Facebook, chats, and forums were the six main types of tools for collaborative writing. Technologies had overall positive effects on students' joint writing qualities, individual writing development, and perceptions of learning tasks. Advantages include prompting group interactions, helping students reflect on their work and identify errors and weakness, boosting learner motivation and confidence, facilitating writing, encouraging students to learn from others, and making the learning process enjoyable. Technologies may be ineffective when technologies were inconvenient to use, when students did not devote adequate effort to planning and reflection, and when students lacked co-responsibility for the writing. This research aims to help researchers and educators understand factors that lead to effective technology enhanced collaborative writing and assist their selection of appropriate technologies and implementation of collaborative writing in and out of class.