Background Sexually transmitted infection (STI) prevention programs can decrease the economic burden of STIs. Foster youth have higher rates of STIs compared with their peers; however, information on direct costs and indirect costs averted by STI testing, treatment, and counseling among foster youth is lacking. Methods This study used data from a comprehensive medical center for foster youth over a 3-year study period from July 2017 to June 2020. Direct and indirect costs averted by testing and treatment of chlamydia, gonorrhea, and syphilis, as well as HIV testing and counseling, were calculated based on formulas developed by the Centers for Disease Control and Prevention and adjusted for inflation. Results Among the 316 youth who received medical services during this time, 206 were sexually active and tested for STIs and/or HIV. Among 121 positive STI test results, 64.5% (n = 78) were positive for chlamydia, 30.6% (n = 37) were positive for gonorrhea, and 5.0% (n = 6) were positive for syphilis. Treatment was provided to all. Overall, $60,049.68 in direct medical costs and $73,956.36 in indirect costs were averted. Conclusions Given the rates of STIs among this population and the economic benefit of STI treatment, it is imperative to continue to provide intensive and comprehensive, individualized sexual health care for foster youth. Traditional care management may miss the opportunity to prevent, identify, and treat STIs that comprehensive wraparound care can achieve. This study suggests that comprehensive wraparound care is a cost-effective way to identify, treat, and prevent STIs among foster youth.