Handwriting is one of the most important essential skills for both literacy and beyond. However, some students have difficulty in writing. Dysgraphia, a disorder of written expression, is a condition where a student's writing skills are below the level expected of their intelligence, age, and education. The main purpose of this study was to examine the effectiveness of a mobile writing application for students with dysgraphia and to determine whether students' writing skills improve after using this application. A mixed method design was employed. This study reveals: 1) the mobile writing application contributed to the acquisition of writing skills (letter formation, spelling, and words) for students with dysgraphia, 2) the percentage of students' on-task duration were in a range of 80% and 100%. When students' writing speed was examined session by session, there was an increase in them all. Students' correct attempts increased session by session and the number of incorrect attempts decreased. Students' line violation tended to decrease session by session.