Screen time is now pervasive in the lives of preschool children, posing potential risks for sleep disturbances and behavioural problems. Therefore, the present study used a questionnaire to survey mothers (M[subscript age] = 35.56 years, SD = 3.62 years) of a total of 571 preschool children (M[subscript age] = 4.70 years, SD = 0.88 years; 44.70% boys) in seven public kindergartens to investigate the association between screen time, sleep quality, and behavioural problems. Results shown that sleep quality partially mediated the relationship between screen time and both hyperactivity attention problems and emotional symptoms. Specifically, screen time was found to increase hyperactivity attention problems and emotional symptoms by reducing sleep quality. However, it was observed that sleep quality did not act as a mediator in the relationship between screen time and peer problems. These findings hold significance in comprehending how screen time and sleep quality are related to behavioural problems in preschool children.