This study examines whether sexually transmitted infection prevention knowledge predicts the acquisition of biologically confirmed sexually transmitted infections among African-American adolescent females. A total of 715 females were recruited from public health clinics in Atlanta, Georgia, and using audio computer-assisted self-interview technology, we assessed for demographics, sexually transmitted infection prevention knowledge, risky sexual behaviors, and sexually transmitted infections. After controlling for demographics and prior risky sexual behaviors, participants with high prevention knowledge were 0.09 times less likely to report sexually transmitted infections, and those with multiple sexual partners were 1.3 times more likely to report sexually transmitted infections. Our findings suggest that the promotion of accurate sexually transmitted prevention knowledge is critical especially among females with multiple sex partners.