The objective of this study is to investigate prevalence and associated factors of commercial sex behaviors and condom use at commercial sex, as well as prevalence of needle sharing among injecting drug users (IDUs) in China. In this study, 162 IDUs were recruited by peer workers in Dazhou, Sichuan and were anonymously interviewed by using a structured questionnaire. Univariate and multivariate logistic regression analyses were performed and interaction between gender and the studied independent variables were tested for significance. The results of this study showed that the male and female respondents, respectively 11.7 and 16.9% were HIV positive; 34.0 and 40.7% engaged in commercial sex and 23.3 and 11.9% shared needles with others in the last six months. Percent using a condom in the last episode of commercial sex was 30.3% for males and 76.2% for females. The multivariate analyses showed that higher drug dosage (OR=0.3, 95% CI: 0.1-0.9) and reduced sexual drive (OR=0.3, 95% CI: 0.1-0.9) were associated with lower likelihood for commercial sex among male IDUs while higher drug dosage (OR=9.1, 95% CI: 1.0-86.0), perceived difficulty in finding a job (OR=5.1, 95% CI: 1.3-20.1) and lack of family support (OR=4.0, 95% CI: 1.1-15.4) were associated with commercial sex among female IDUs. Similarly, unknown HIV status (OR=8.2, 95% CI: 1.7-9.2) and having a regular sex partner (OR=3.7, 95% CI: 1.3-10.9) was associated with needle sharing. It is concluded that male and female IDUs were sexually active and often engaged in commercial sex. Drug dosage and reduced sexual drive were relevant but did not stop commercial sex behaviors. More supportive social environment is required to prevent female IDUs to enter sex work.