Research Findings: Recent research has validated the power of evidence-based preschool interventions to improve teaching quality and promote child school readiness when implemented in the context of research trials. However, very rarely are follow-up assessments conducted with teachers in order to evaluate the maintenance of improved teaching quality or sustained use of evidence-based curriculum components after the intervention trial. In the current study, we collected follow-up assessments of teachers 1 year after their involvement in the REDI (REsearch-based, Developmentally Informed) research trial to evaluate the extent to which intervention teachers continued to implement the REDI curriculum components with high quality and to explore possible preintervention predictors of sustained implementation. In addition, we conducted classroom observations to determine whether general improvements in the teaching quality of intervention teachers (relative to control group teachers) were sustained. Results indicated sustained high-quality implementation of some curriculum components (the Promoting Alternative THinking Strategies curriculum) but decreased implementation of other components (the language/literacy components). Sustained intervention effects were evident on most aspects of general teaching quality targeted by the intervention. Practice or Policy: Implications for practice and policy are discussed.