For over four decades family therapy research and family centered evidence-based therapies for justice-involved youths have played influential roles in changing policies and services for these young people and their families. But research always reveals challenges as well as advances. To be sure, demonstration that an evidence-based therapy yields better outcomes than comparison treatments or services as usual is an accomplishment. But the extraordinary complexity embedded in that assertion feels tiny relative to what we are now learning about the so-called transfer of evidence-based treatments to real world practice settings. Today's family therapy studies continue to assess outcome with diverse samples and presenting problems, but research and funding priorities also include studying particular treatments in nonresearch settings. Does an evidence-based intervention work as well in a community clinic, with clinic personnel? How much of a treatment has to change to be accepted and implemented in a community clinic? Perhaps it is the setting and existing procedures that have to change? And, in those cases, do accommodations to the context compromise outcomes? Thankfully, technology transfer notions gave way to more systemic, dynamic, and frankly, more family therapy-like conceptions of the needed process. Implementation science became the more sensible, as well as the theoretically and empirically stronger overarching framework within which the evidence-based family based therapies now operate. Using the example of Multidimensional Family Therapy, this article discusses treatment development, refinement, and implementation of that adapted approach in a particular clinical context-a sector of the juvenile justice system-juvenile detention.