Technical assistance (TA) is a tailored approach to capacity building that has grown in use across diverse settings over the past two decades, particularly in the domains of health improvement, child welfare, youth development, and education. In practice, TA services often include a combination of activities (e.g., coaching, professional development, site visits, and resource sharing) and vary in dosage, modality, and numerous other dimensions. While tailoring to recipient needs holds significant value, the individualized nature of TA creates challenges for assessing the effectiveness of TA. The difficulty of determining what contributes to TA outcomes is amplified when TA delivery is largely reactive (rather than proactive) and unaccompanied by a systematic approach to planning, delivery, and evaluation. Logic models are a well-established tool and a straightforward way to make TA more systematic. In this article, we introduce the TA Effectiveness Logic Model as a skeletal framework to guide systematic TA planning, delivery, and evaluation. The TA Effectiveness Logic Model graphically presents the rationale and expectations for how TA works in a setting. We describe two types of TA effectiveness logic models: basic and contextual. In addition, we offer a case example from work based on a national training and TA center to illustrate both types of logic models. Lastly, we discuss practical implications of TA effectiveness logic models for TA collaborators (funders, training and TA center administrators, TA providers, TA recipients, and researchers). Routinizing the use of TA effectiveness logic models has benefits for both the science and practice of TA.