BackgroundThere is a growing body of research studying the impact sleep has on attention among typically developing (TD) children, but research is lacking among autistic children. AimsThe present study aimed to explore, for the first time, differences in (1) attention, (2) sleep parameters among primary school-aged Singaporean autistic children (N = 26) and Singaporean TD children (N = 20), and with UK autistic (N = 11) and UK TD children (N = 16), and (3) the impact of sleep on attention. Methods and proceduresActigraphy was used to objectively assess sleep, and a Continuous Performance Task was used to measure attentional domains. Outcomes and resultsThere were inconclusive findings indicating that autistic children had poorer sustained attention than TD children. Although autistic children did not display more sleep difficulties than TD children, they showed shorter actual sleep duration (Singapore ASD = 7:00 h, UK ASD = 7:35 h, p < .01) and longer sleep latency (Singapore ASD = 30:15 min, UK ASD = 60:00 min, p < .01) than clinical recommendations. Sleep difficulties were also present among Singaporean and UK TD children. Both TD groups had less actual sleep duration than recommended (Singapore TD = 6:32 h, UK TD = 8:07 h). Singaporean TD children had sleep efficiency below recommended criterion (78.15%). Sleep impacted attention across all groups, but effects were different for autistic and TD groups. Conclusions and implicationsThe study highlighted the importance for practitioners and carers to adopt a child-centred approach to assessing sleep and attentional difficulties, especially among autistic children due to the high variability in performance within the group. The impact of cultural and school-setting differences on sleep was also raised.