Objectives Preterm birth is associated with altered pubertal timing, but the effect on pubertal duration has rarely been assessed. Here, we tested the hypothesis that preterm birth is associated with shorter duration of puberty among girls in Hong Kong where preterm birth has little social patterning. Methods In the population‐representative Chinese birth cohort “Children of 1997”, we used multivariable linear regression to assess the association of preterm status (≤36 completed gestational weeks, n = 170; term birth 37–42 gestational weeks, n = 3476) with duration of puberty, adjusted for parent's highest education, mother's place of birth, maternal smoking during pregnancy, gestational diabetes, preeclampsia, and mother's age of menarche. Results The mean duration from thelarche to menarche was 2.53 years. Preterm girls had a shorter duration from thelarche to menarche by 2.6 months, 95% confidence interval 0.5–4.7 months. Age of menarche did not differ by preterm status but preterm girls had later thelarche. Preterm birth was not associated with a shorter duration from pubarche to menarche. Conclusions Preterm births may be associated with shorter duration of puberty from thelarche to menarche, possibly through effects of in utero estrogen exposure, the drivers of thelarche, or the drivers of pubertal duration/progression, with potential implications for subsequent risk of cardiovascular disease and hormonal cancers.