Severe involvement of the nail matrix can lead to extensive dystrophic changes of the nail plate. Topical or intralesional corticosteroids, photochemotherapy, oral retinoids, and methotrexate (MTX) are among the therapies used. Treatment of severe psoriatic nail disease is often unsatisfactory. We report a case of severe psoriatic nail dystrophy involving all 20 nails successfully treated by low dose MTX. A previously healthy 11-year-old girl presented with painful deformity involving all 20 nails that developed over a one-month period. Examination revealed geographic and fissured tongue, as well as severe nail dystrophy of all 20 nails characterized by erythematous swelling of the nail folds, yellowish discoloration of nail plates with pitting, severe crumbling and destruction, transverse depressions, prominent oil spots, and swelling of proximal nail. Topical clobetasol propionate and calcipotriol were tried first but the nail dystrophy continued to progress. Low dose of MTX (5 mg per week) was initiated. The response was fairly satisfactory with emergence of normal plate proximally as early as 4 weeks; complete resolution of the severe nail dystrophy was achieved after 9 and 13 months of MTX therapy for fingers and toes, respectively. The present case illustrates that weekly low dose oral MTX may be a good treatment option for severe psoriatic nail dystrophy in patients without other contraindications for MTX therapy.