Background: The assessment of the intelligence quotient (IQ) in children with autism spectrum disorder (ASD) is important to plan a detailed therapeutic-educative programme. The aim of the study was to evaluate the usefulness of the Psychoeducational Profile-third edition (PEP-3) to estimate the general cognitive development of children with ASD. Method: We recruited 30 children with ASD assessed with the Leiter International Performance Scale-Revised (Leiter-R) and the PEP-3. We compared the IQ of the Leiter-R with the developmental level (DL) of PEP-3. Results: The findings showed a significant positive correlation between IQ with DL of the cognitive verbal/pre-verbal (P = 0.0005), DL of the area of expressive language (P = 0.0004), DL of the area of receptive language (P = 0.0001), DL of fine motor (P = 0.0066), DL of gross motor (P = 0.0217), DL of visuo-motor imitation (P = 0.02), DL of communication (P = 0.0001) and DL of motor (P = 0.0063). Conclusions: These findings show that the DLs could be considered as indicators of cognitive functioning in ASD.