Children who engage in chronic problem behavior can present challenges for their early childhood teachers, and are more likely to develop negative relationships with these and other adults with whom they interact. Unfortunately, children who develop negative relationships with their teachers early in their school careers are more likely to have later academic and behavioral problems than children who have positive, supportive relationships. The salience of interactions between teachers and young children highlights the need for interventions that target building positive teacher-child interactions and increase the likelihood that these interactions are developmentally appropriate and supportive of children's emotional and behavioral growth, as well as assessment tools to evaluate the effectiveness of these interventions. The purpose of this article is to describe the Teacher-Child Interaction Direct Observation System ("TCIDOS"), an observation system designed to capture teacher and child behaviors during classroom interactions to evaluate the effectiveness of a classroom-based intervention targeting improvements in teacher-child interaction patterns. Following a description of our conceptual framework and the development of the "TCIDOS," we discuss preliminary reliability findings and future research directions as well as challenges inherent to collecting direct observational data in classroom settings.