This study aimed at investigating the effect of twitter on EFL writing and whether twitter has an effect on: ideas and content, organization, voice and style. This study followed a pretest-posttest experimental-control group design. Two intact classes were chosen to be the sample of the study from level four: one class to be an experimental group and the other class to be the control group. Instrument of the study was an EFL writing test. Students in both the experimental and control groups were pre-tested on their writing skills using the EFL writing test. Students in the experimental group were taught using Twitter and students in the control group were taught using the traditional method of teaching writing. Finally, students in both groups were post-tested using the EFL writing test. The study showed that the experimental group outperformed the control group on post-testing of writing. This difference can be attributed to using Twitter in teaching writing.