The current study examined 12-month outcomes for girls enrolled in an implementation trial of Treatment Foster Care of Oregon (TFCO) in England. In addition to examining changes from pre-treatment to post-treatment, we also compared results for girls enrolled in the England implementation trial to girls enrolled in two randomized controlled trials (RCTs) of TFCO in the United States. The England TFCO sample included 58 girls in foster care between the ages of 12 and 16. The US TFCO intervention samples included 81 girls between the ages of 13 and 17 who were referred to out-of-home care due to chronic delinquency. Results indicated improvement in offending, violent behavior, risky sexual behavior, self-harm, and school activities for girls enrolled in the England implementation trial. The effect sizes of these results were similar to those obtained in the US RCTs, with the exception of substance use which showed significant decreases for girls enrolled in the US RCTs, but not for girls enrolled in the England implementation trial. These results, in combination with other cross-cultural findings, support the notion that TFCO might be relevant across US and European cultures.