Female injecting drug users who are sex workers (IDUFSWs) are an important bridge population in HIV transmission. Few studies have investigated the associations between mental health, interpersonal problems, and HIV-related risk behaviors among injecting drug users who are sex workers. A total of 234 non-institutionalized injecting drug users who are sex workers were recruited using the snowball method. Multiple logistic regression was used for data analysis. A high prevalence of mental health (depression, hopelessness, pessimism) and interpersonal (lack of social support and submissive gender power) problems was reported. Optimism and social support were negatively associated with inconsistent condom use during sex work in the last six months (adjusted odds ratios [AOR] = 0.62-0.86); positive associations were observed for depression, hopelessness, pessimism, and gender power (AOR = 1.17 to 1.68). Injecting with others' used syringes in the last six months was negatively associated with social support (AOR = 0.75) and positively associated with hopelessness and gender power (AOR = 1.13-1.27). In two summary models using all significant independent variables as candidates, optimism was negatively (OR = 0.62) and submissive gender powers were positively (OR = 1.67) associated with inconsistent condom use during sex work; submissive gender power was positively associated with injecting with others' used syringes (OR = 1.38). HIV interventions targeting mental health and interpersonal problems are needed among injecting drug users who are sex workers.