BACKGROUND Obese adults have a higher risk of obstructive sleep apnoea (OSA); however, the relationship between childhood obesity and adult OSA risk is unclear. Objectives This study aimed to examine overweight/obesity (OW) in childhood and risk of OSA in middle age. METHODS Childhood OW status was classified as never OW, weight cycling, persistent OW and incident OW. After 35 years of follow-up, high risk for OSA was determined by a positive score in ≥2 domains on the Berlin Questionnaire with obesity removed from scoring. RESULTS At initial assessment, mean (SD) age was 9.9 (2.9) years, and 23.9% were OW. Overall, 25.7% had scores indicating a high risk for OSA. Compared with participants who were never OW, those with persistent OW and incident OW were 1.36 (95%CI: 1.04-1.77) and 1.47 (1.11-1.96) times more likely to be high risk for OSA, after adjustment for multiple risk factors and adult OW status. Participants with an OW duration of 1-4 years, 5-8 years, and 8+ years were 0.96 (0.44-2.09), 1.20 (0.70-2.04) and 1.52 (1.22-1.90) times more likely to be high risk for OSA compared with those who were never OW (P for trend: 0.0002). CONCLUSIONS These results suggest that childhood OW is associated with a high risk of OSA in middle age.