The current study investigated early temperament in 54 infants at familial high-risk of ASD and 50 controls. Parental report of temperament was assessed around 7, 14 and 24 months of age and diagnostic assessment was conducted at 3 years. The high-risk group showed reduced Surgency at 7 and 14 months and reduced Effortful Control at 14 and 24 months, compared to controls. High-risk infants later diagnosed with ASD were distinguished from controls by a temperament profile marked by increased Perceptual Sensitivity from the first year of life, and increased Negative Affect and reduced Cuddliness in the second year of life. Temperament may be an important construct for understanding the early infant development of ASD.