Early puberty is associated with adverse health outcomes over the life course, and Black and Hispanic girls experience puberty earlier than girls of other racial/ethnic backgrounds. Neighborhood racial and economic privilege may contribute to these disparities by conferring differential exposure to mechanisms (e.g., stress, obesity, endocrine disruptors) underlying early puberty. We examined associations between neighborhood privilege, measured by the Index of Concentration at the Extremes (ICE), and age at pubic hair onset (pubarche) and breast development onset (thelarche) in a large multiethnic cohort. A cohort of 46,299 girls born 2005-2011 at Kaiser Permanente Northern California medical facilities were followed until 2021. Pubertal development was assessed routinely by pediatricians using the Sexual Maturity Rating scale. ICE quintiles for race/ethnicity, income, and income + race/ethnicity were calculated using American Community Survey 2010 5-year estimates and linked to census tract at birth. We fit multilevel Weibull regression models accommodating left, right, and interval censoring for all analyses. ICE measures were monotonically associated with pubertal onset, with the strongest associations observed for ICE-race/ethnicity. Adjusting for maternal education, age at delivery, and parity, girls from the least versus most privileged ICE-race/ethnicity quintiles were at increased risk for earlier pubarche (hazard ratio: 1.30, 95% confidence interval: 1.21, 1.38) and thelarche (hazard ratio: 1.45, 95% confidence interval: 1.36, 1.54). These associations remained significant after adjusting for girls’ race/ethnicity and childhood body mass index. Additionally, adjustment for ICE partially attenuated Black-White and Hispanic-White disparities in pubertal onset. Neighborhood privilege may contribute to pubertal timing and related disparities.