We evaluated the potential role of birth characteristics in the etiology of early-onset meningioma. Leveraging a population-based linkage of California birth records (from 1978 to 2015) and cancer registry data (from 1988 to 2015), we identified 362 nonmalignant meningioma cases aged 0-37 years and selected 18 100 controls matched on year of birth. Cases and controls were compared with regard to birth characteristics, with adjusted odds ratios (ORs) and 95% confidence intervals (CIs) estimated from unconditional multivariable logistic regression models. We also conducted stratified analyses by race/ethnicity and age. Female sex (compared to male: OR = 1.43, 95% CI: 1.16 to 1.79; P < .01) and Black race (compared to White: OR = 1.46, 95% CI: 1.02 to 2.07; P = .04) were associated with higher risk of meningioma. Higher birth order (OR = 0.90, 95% CI: 0.81 to 0.99 per additional birth position; P = .04) was associated with a lower risk. No significant associations were observed between birthweight, gestational age, delivery mode, maternal age, or maternal education and meningioma risk. In the non-Latino White subgroup, higher birthweight was associated with a higher risk of meningioma (OR = 1.20, 95% CI: 1.02 to 1.41 per 500 grams; P = .03), but this was not recapitulated in the Latino subgroup. In age-stratified analyses, female sex was a risk factor for those diagnosed at the age of 20-37 years but not among younger individuals. In this large population-based study less prone to selection and recall bias, higher birth order was associated with a reduced risk of early-onset meningioma, while female sex and Black race were linked to an increased risk. There were also indications of differential associations by race/ethnicity and age of diagnosis.