In the Taiwan EFL context particularly, little attention has been given to investigating the effects of wikis on EFL writing performance. Therefore, this study suggests a wiki-based collaborative writing activity in the writing process of creative English writing. In addition, the students' perceptions of wiki collaborative writing were also measured. In this one-group pretest-post-test study, 32 learners at a public university in central Taiwan were invited to participate. The participants were selected using convenience sampling, a non-probability sampling technique. Instruments used to collect the data were online student background questionnaires, writing pre- and post-tests, and a student online questionnaire on wiki collaborative writing. The data from the wiki collaborative writing questionnaire were analyzed using descriptive statistics. The result of the study is expected to be able to enhance students' writing performance and to encourage them to have strong motivation and good attitudes toward English writing. The students enjoyed being involved in online collaborative writing and learned to give comments and receive feedback in groups. It is thought to be a useful practice to enable students to socially interact to gain more knowledge, insights, and experience.