Between 2012 and 2018, the U.S. Department of Education invested nearly $350 million in 22 Comprehensive Technical Assistance (TA) Centers operating across the nation. These Centers were charged with delivering TA that builds the capacity of state education agencies (SEAs) to support local educational agencies (LEAs) in improving student outcomes. Centers were given broad discretion in interpreting and enacting this mandate. This evaluation sought to address the open questions about how the Centers designed and implemented the TA, what challenges they encountered, and what outcomes they achieved. With thorough documentation of how this process played out, stakeholders will be in a better position to inform future program improvement. Key takeaways from the study include: (1) Overall, Centers and their TA recipients reported that the Centers' TA improved the capacity of SEAs to meet their goals; (2) Centers shared similar approaches to the design and implementation of their TA. Those Center practices perceived to be instrumental to building capacity included: engaging a broad array of stakeholders to provide input on policy; providing products and tools for SEA staff to use as they took greater ownership of policy design and implementation; imparting organizational practices and structures resilient to SEA turnover and policy shifts; and flexibly adapting TA in response to changing priorities and needs. (3) Centers and their TA recipients pointed to a few areas for program improvement, including clarification of the Centers' role and expected outcomes related to their work with LEAs, and further guidance for SEAs about how best to use the Centers. Overall, the evaluation found that Centers shared similarities in their approaches to the design and implementation of their work, and Centers and key TA recipients reported that the work generally helped build SEA capacity. These two projects are not necessarily representative of all Center projects, but were selected to bring the overall findings in this report more to life while also recognizing the unique combinations of needs, strategies, challenges, and outcomes that may make up each project. This evaluation's findings are consistent with the findings of the prior national evaluation of the Centers, published in 2011. [For the 2011 report, see ED523401. For the study highlights of the 2019 report, see ED599102. For the appendices for the 2019 report, see ED599104.]