In language acquisition, writing is the most challenging skill that English learners must master. Students often struggle at the beginning of their writing process with idea generation. Due to students' low academic achievement and their struggles, online mind mapping is suggested as a useful tool to support language students' brainstorms and idea organization during the writing process. The purpose of this mixed-method study was to investigate how online mind mapping can help students collaboratively brainstorm and organize their ideas during the prewriting process. This study focused on the effects of online mind-mapping intervention on student academic writing performance and perceptions in a Read-Think-Write 2 class at FPT University, a private university in Southern Vietnam. In the study, the independent variable was online mind mapping, and the dependent variables were student idea elaboration and organization. For the treatment group, mind mapping was part of instruction for the course. Data collection included a presurvey, a questionnaire and a posttest from the mind-mapping training session, class assignments, a coursework inventory, and the final writing exam grades from their previous ERW411 class. Findings from this study indicated that there was a statistically significant relationship between student understanding of online mind mapping and their brainstorming and organization. The results also revealed that there were no statistically significant differences in idea elaboration and organization between the two groups, but the mean for students from the treatment group were slightly higher than the ones from the control group. Students from both groups agreed that the coursework was somewhat interesting and useful, and they believed that they could succeed in the course. Eighty percent of interviewed students shared their positive attitudes toward the effects of online mind mapping in the prewriting process, whereas all of them expressed a desire to continue using online mind mapping in future courses. This study provided an evidence-based framework for implementing technology-assisted tools, namely online mind mapping, into language acquisition. Educational practitioners should enable more instructional technologies to support language teaching. Additional research with a larger number of participants in different educational settings would further expand the findings with more effective instructional strategies for teaching and learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]