In a national, facility-based survey of female sex workers in 14 cities of Iran (N = 872), HIV prevalence was measured at 4.5 % (95 % CI, 2.4–8.3) overall and at 11.2 % (95 % CI, 3.4–18.9) for FSW with a history of injection drug use. Using methods to correct for biases in reporting sensitive information, the estimate of unprotected sex in last act was 35.8 %, ever injecting drugs was 37.6 %, sexually transmitted disease symptoms was 82.1 %, and not testing for HIV in the last year was 64.0 %. The amount of bias correction ranged from <1 to >30 %, in parallel with the level of stigma associated with each behavior. Considering the current upward trajectory of HIV infection in the Middle East and North Africa region, as well as the ongoing high level of risky behaviors and considerable underreporting of many such behaviors in surveys, bias corrections may be needed, especially in the context of Iran, to obtain more accurate information to guide prevention and care responses to stop the growing HIV epidemic in this vulnerable group of women.