There is growing interest in telomere length as an indicator of current and future health. Although early childhood is a period of rapid telomere attrition, little is known about the factors that influence telomere biology during this time. Adult research suggests that telomere length is influenced by psychological characteristics. This study's goal was to test associations among repeated measures of temperament and telomere length in a community sample of children (N = 602; 52% male, 73% non-Hispanic White, middle-to-high socioeconomic status) from infancy to age 3 years. Relative telomere length was assessed from DNA in saliva samples collected at infancy (M = 8.4 months), 2 years (M = 24.9 months), and 3 years (M = 37.8 months). Temperament was assessed via maternal report questionnaires administered at infancy (Infant Behavior Report Questionnaire-Revised) and ages 2 and 3 years (Early Childhood Behavior Questionnaire). Temperament was operationalized in two ways: using the established domains of negative affectivity, surgency/extraversion, and regulation/effortful control and using person-centered scores that identified three groups of children with similar profiles across domains (emotionally and behaviorally regulated; emotionally and behaviorally dysregulated; introverted and overcontrolled). Analyses revealed that greater regulation/effortful control was associated with longer telomere length across time points. Additionally, higher surgency/extraversion, beginning in infancy, was associated with decreased rate of telomere attrition. There were no sex differences in the relations between temperament and telomere measures. These findings suggest that, as early as infancy, temperament may influence telomere biology, with a potential protective effect of positive temperament characteristics on telomere erosion. (PsycInfo Database Record (c) 2023 APA, all rights reserved).