Adult obesity increases risks of renal cell carcinoma (RCC). This study investigated if birth weight, child body mass index (BMI) and height are associated with adult RCC. The study included 301,418 children (152,569 boys) from the Copenhagen School Health Records Register born 1930-1985 with measured weights and heights at ages 7 to 13 years. Birth weight was obtained by parental report. BMI and height were transformed to z-scores, and BMI was categorized as normal BMI or overweight. RCC was identified by linkage to the Danish Cancer Registry. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated by Cox proportional hazards regression. During follow-up, 1010 individuals (680 men) were diagnosed with RCC. BMI and height were positively associated with RCC with no significant sex-differences (age 13: HR = 1.14, 95% CI 1.06-1.23 per BMI z-score, HR = 1.12, 95% CI 1.05-1.20 per height z-score). Compared to children with normal BMI at ages 7 and 13 years, children with overweight only at age 13 had higher risks of RCC (HR = 1.67, 95% CI 1.24-2.26). Compared to children with average growth in height, persistently taller-than-average children (HR = 1.06, 95% CI 1.03-1.10) and children who changed from average to above-average height (HR = 1.08, 95% CI 1.01-1.15) had increased risks of RCC. Birth weight was positively associated with RCC (HR = 1.12, 95% CI 1.05-1.20 per 500 grams). Birth weight, childhood BMI and height were positively associated with RCC risk in men and women.