Previous studies have reported mixed results regarding the association between age at menarche and environmental tobacco smoke exposure, both prenatally and during early childhood; however, few studies have had data available during both time periods. The present study examined whether exposure to prenatal tobacco smoke (PTS) via maternal smoking during pregnancy or childhood environmental tobacco smoke (ETS) was associated with age at menarche in a multi-ethnic birth cohort. With the uniquely available prospectively collected data on body size and growth at birth and in early life, we further examined whether the association between PTS and ETS exposure and age at menarche was mediated by these variables. From 2001 to 2006, we recruited 262 women born between 1959 and 1963 who were enrolled previously in a New York City site of the National Collaborative Perinatal Project. Mothers who smoked during pregnancy vs. those who did not were more likely to be White, younger, have more education and have lower birthweight babies. Daughters with heavy PTS exposure (≥ 20 cigarettes per day) had a later age at menarche (>12 years vs. ≤ 12 years), odds ratio (OR) =2.1 [95% confidence interval (CI) 0.9, 5.0] compared with daughters with no PTS. Daughters exposed to only childhood ETS had a later age at menarche, OR=2.1 [95% CI 1.0, 4.3], and those exposed to PTS and ETS combined had a statistically significant later age at menarche, OR=2.2 [95% CI 1.1, 4.6] compared with daughters with no PTS and no ETS. These results did not change after further adjustment for birthweight and postnatal growth suggesting that exposure to PTS and ETS is associated with later age at menarche even after considering possible relationships with growth.