Few studies have investigated the potential impact of sickle cell anaemia (SCA) on temperament. The aim of the current study was to investigate temperament in preschool children with SCA and to establish the reliability of the Children's Behaviour Questionnaire (CBQ) in this population. The CBQ, a parent-report measure of temperament, was completed by parents of 21 preschool children with SCA and a control group of parents of typically developing children, matched for age, ethnicity and socioeconomic status. A significant difference between groups was identified for the dimension of negative affectivity only, with specific differences observed in the discomfort subdomain. Patients with a greater number of hospital admissions in the previous year were reported to have higher levels of discomfort. Preschool children with SCA are reported to have higher rates of negative affectivity, particularly discomfort. Future research is required to investigate the potential influence of dysregulated negative emotions and discomfort on disease management and quality of life throughout childhood. © Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.