Anxiety is one of the most common psychiatric disorders among children yet characterized by lower use of mental health services. Preventive efforts have demonstrated promise in the ability to reduce anxiety symptoms. However, as evidence-based interventions move into real-world settings, there is a need to systematically examine potential implementation factors that may affect program outcomes. The current study investigates the relations between different aspects of implementation and their effect on outcomes of a school-based preventive intervention targeting anxiety symptoms. Specifically, the study examines: (1) the measurement of quality of delivery, (2) specific relations among implementation components, (3) relations between these facets and anxiety program outcomes. Implementation data were collected from nine school-based mental health staff and observer ratings. Program outcomes (pretest and immediate posttest) were measured from 59 participants and their parents (mostly mothers) in the intervention condition. Implementation components included adherence, quality of delivery, time spent, participant responsiveness, and perceived usefulness of program materials. Program outcomes included child-reported emotional expressivity, physiological hyperarousal, negative cognitions, social skills, self-efficacy, and child and parent reported levels of child anxiety. Study findings indicated that quality of delivery was best captured as two facets: skillful presentation and positive engagement. Adherence and quality of delivery were associated with greater participant responsiveness, although time spent was not. Significant relations were found between some implementation components and some program outcomes. Further efforts can be used to optimize the translation of evidence-based programs into real-world settings.