Objectives In China, considerable stigma surrounds sexual activity, contraception use and abortion among young unmarried women, and sex work remains illegal. This study examines characteristics of adolescent female sex workers (FSWs) associated with contraceptive use and abortion in Kunming, China. Methods This cross-sectional study was conducted between July 2010 and February 2011. Adolescent FSWs were recruited using snowball and convenience sampling. We present descriptive statistics, comparative analyses of socio-demographic and reproductive characteristics of respondents who had or had not used modern contraceptives, and assessed factors associated with prior abortion using simple odds ratios (ORs) and multivariate logistic regression adjustments. Results Twenty-seven percent of adolescent FSWs had never used any modern contraceptive. Condoms (69%) and oral contraceptives (38%) were most commonly reported, and less than 3% had ever relied on an intrauterine device. We found low rates of dual protection (34%). About half of the respondents reported one or more lifetime abortions. Inconsistent condom use, frequent alcohol use and longer-term cohabitation were associated with prior abortion. Conclusions Low consistent utilisation of modern contraceptives and of dual protection, and high rates of abortion, highlight the urgent need for early contact and continuous provision of comprehensive reproductive health services for adolescent FSWs.