Sibling relationship and personality characteristics of 87 pre-school sibling dyads were measured twice one year apart. Using the Inventory of Child Individual Differences (Halverson et al., 2003), mothers and fathers rated their children’s personality traits. Parent-perceived warmth, agonism, and rivalry/competition in sibling relationship were assessed by Parental Expectations and Perceptions of Children’s Sibling Relationships Questionnaire (Kramer, 2001). The results suggest that (a) parental ratings of both siblings’ personality, and (b) match in their personalities are contemporaneously and longitudinally associated with parent-perceived sibling relationship dimensions. The relations were more consistent for negative than positive aspects of sibling relationship. Older siblings’ personality contributed somewhat more to the relationship than individual characteristics of younger ones. Across the cross-rater analyses and measurement occasions, disagreeableness was most consistently linked to sibling relationship. The role of siblings’ (dis)similarity in high or low end of particular personality traits in their relationship quality is also highlighted.