Few studies have explored autism spectrum disorder (ASD) screening in the first year of life. The current investigation examines the psychometric properties of the Infant-Toddler Checklist starting in the first year of life in a sample at elevated and average risk for ASD based on family history. 283 participants were followed from 6 to 36 months, when diagnostic outcome was determined. The results indicated low to moderate sensitivity, specificity, and positive predictive value across ages for broadly distinguishing any delays from typical development, as well as for more narrowly discriminating children with ASD from those who were typically developing. Implications for utilizing ASD screening tools in the first year of life with high risk samples are discussed.