Objective: The present study investigates spelling errors in students' with intellectual disabilities (grades 3 to 9,  primary to pre-vocational) written discourse. Method: For this descriptive-analytic study, the subjects were chosen through random sampling among 4 schools (2 boys’ and 2 girls’). Four pictorial stories were used and all students in the class were asked individually to write stories for the provided picture series. Results: After collecting the data (2407 clauses and 10861 words), they were analyzed based on linguistic processes. 518 token of spelling errors were derived which were described considering phonetics, phonology, and orthography: Errors were classified into four basic processes: deletion, wrong use of letters, addition, and metathesis the frequency of which follows respectively: 36 %, 32%, 24%, and 8%. Conclusion: Clinical implications of spelling errors in students with intellectual Disabilities were discussed.