BACKGROUND Mirror writing is unusual handwriting, in which the writing is in the opposite direction to normal, with reversed letters can be effortlessly read using a mirror. Studies reported that the condition can occur temporarily during the normal development of writing skills in children, and can also could occur in children with developmental delays. In adults, it can be acquired after a brain lesion. CASE REPORT A right-handed 19-year-old Saudi woman presented with progressive-onset mirror writing in both hands, and with writing both languages, Arabic and English. The condition was transient and had gradually worsened over the previous 3 years. Recently, it was continuous. She denied a history of alcohol or illicit drug abuse. There was no history of head injury, dyslexia, learning disabilities, or transient mirror writing during writing development in her early school-age years. There was no similar condition in her family. The neuropsychological assessment was normal. Laboratory and imaging were performed to rule out structural lesions, and no underlying etiology was found. After 2 years of follow-up, the patient did not have other associated neuropsychological symptoms, and mirror writing was persistent. CONCLUSIONS Mirror writing in this case was in the right-handed, healthy young woman and was idiopathic. The condition was benign and the 2-year follow-up neuropsychological assessment was normal. The patient lived with the condition, depending on computer typing instead of handwriting, and she had very good academic performance in the university. We suggest that physicians have to diagnose this condition by exclusion and reassure and support the patients to cope with the condition.