The aim of the present study was to investigate the evolution of emotion regulation competencies in sexually abused preschoolers. Children's emotion regulation abilities and their emotional lability and negativity were assessed shortly after disclosure of sexual abuse and one year later, and compared to those of non-abused children. A sample of 47 sexually abused (37 girls, 10 boys) and 74 non-abused children (54 girls, 20 boys), aged 3–7 years (M = 56.83 months; SD = 9.55), participated in the study. Parents and daycare educators or teachers completed the Emotion Regulation Checklist (Shields & Cicchetti, 1997) and an adapted version of the History of Victimization Form (Parent & Hébert, 2006). Parents reported more emotional lability/negativity in sexually abused children, with an increase of difficulties and a larger difference between groups at follow-up assessment conducted one year later. Parents of sexually abused children, especially those of boys, also reported lower emotion regulation competencies in their child than parents from the comparison group. According to educators, victims of sexual abuse had lower emotion regulation abilities, but their lability/negativity tended to subside over time. Various hypotheses are proposed to explain the differences between sexually abused boys’ and girls’ emotion regulation competencies, and between the two informants. Clinical implications are also discussed. Emotion regulation seems to be an important dimension to consider in future interventions for this specific population.