The present study aimed to investigate the test-retest reliability of the Wechsler Intelligence Scale for Children-Fourth edition (WISC-IV) in a sample of 138 children with autism spectrum disorder (ASD) from a child psychiatric clinic in Tokyo, Japan. The stability coefficient of the Full Scale Intelligence Quotient (FSIQ), which is composed of four indices, was very high at 0.83, while those of the Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PRI), Working Memory Index (WMI), and Processing Speed Index (PSI) individually were moderate to high, ranging from 0.62 to 0.79. Comparisons among three age groups revealed that the coefficients for children aged 5 to 7 years tended to be lower than those for children aged 11 years and older. With respect to relative strengths and weaknesses between index scores, approximately half of children did not exhibit the same trend in the second test. These results revealed that the FSIQ and index scores are stable in the long term in children with ASD aged 11 years and older, and that the PSI and discrepancies in index scores are less stable. Thus, practitioners should take into account ecological information and the test-taking behaviors of children when interpreting WISC-IV results for children with ASD.