Writing is one of the two basic methods of communication, and students, during their studies and even graduates, may have to write a report and plan a strategy in the workplace. Therefore, improving writing skills in general and English writing skills, in particular is essential. In the process of learning writing skills at university, students often encounter both objective and subjective difficulties. To improve students’ English writing skills, the author conducted a study in which collaborative writing was employed to assess students’ writing ability. This study was completed within 15 weeks with 60 students in two classes in the same Department of Foreign Languages at Dong Nai Technology University. To evaluate the method’s effectiveness, the author compared the pre-test and post-test results. At the end of the semester, the author also collected students’ opinions on collaborative writing activities. The results show that the student’s writing skills have improved through collaborative writing, considered better than individual writing. Most students also affirmed their interest in this activity and pointed out many advantages.