Objective: Handwriting difficulties are a common educational problem in mentally retarded students. The aim of this survey is producing an instrument for handwriting evaluation and executing it on the mentally retarded students.

Materials & Methods: In this descriptive and cross – sectional research which is a relationship and validity assessment study, one hundred and twenty six mentally- retarded students (53 girls and 73 boys) ranging from 9 to 19 years old from two exceptional children schools in Shahr-e-rey participated. A handwriting check-list made by the researcher was executed on all of the students. Data were analyzed by use of independent T test, Mann Whitney test and Spearman correlation.

Results: Executing handwriting checklist on the mentally-retarded students showed that there is not a significant relationship between handwriting and laterality (P=0.196), sex (P=0.487) and age (P=0.449). There is significant relationship between handwriting and grade (r=0.448, P<0.005), but between different grades wasn’t seen significant difference. The most common damaged legibility component in the sample was “interruption during writing words” with 81 percent and the least common was “spacing between letters and words” with 34.9 percent.

Conclusion: The rate of legibility components difficulties in handwriting of mentally-retarded students indicates that handwriting difficulties in exceptional schools needs professional attention.