The current study examined 12-month outcomes for girls enrolled in an implementation trial of Multidimensional Treatment Foster Care (MTFC) in England. In addition to examining changes from pretreatment to posttreatment, we also compared results for girls enrolled in the England implementation trial to girls enrolled in a randomized controlled trial (RCT) of MTFC in the United States. The England MTFC sample included 58 girls in foster care between the ages of 12 and 16 years. The U.S. MTFC intervention sample included 81 girls between the ages of 13 and 17 years 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 U.S. RCT, with the exception of substance use, which showed significant decreases for girls enrolled in the U.S. RCT but not for girls enrolled in the England implementation trial. These results, in combination with other cross-cultural findings, support the notion that MTFC might be relevant across U.S. and European cultures. Abstract published by arrangement with Taylor and Francis.