With increasing rates of children with challenging behaviors in preschool environments, preschool teachers need interventions that are feasible and simple to implement. Check-In/Check-Out (CICO) is a behavioral intervention designed for students who require additional supports in classroom settings. It is a secondary tiered intervention in the three-tiered model of prevention: Positive Behavioral Interventions and Supports (PBIS). For early childhood settings, PBIS has been modified to meet the needs of young children and their teachers and families: EC-PBIS. In general, CICO provides children with positive consequences contingent upon appropriate behaviors, such as stickers or checkmarks throughout the day, and a reward at the end of the day for reaching an agreed upon number of stickers or checkmarks. This positive reinforcement intervention includes built-in one-on-one attention for a child's appropriate behaviors, which is effective for many children who exhibit attention seeking behaviors. Behavioral expectations are clearly defined and stated in positive wording that children can understand. One essential element of CICO is increased positive adult contact. Some children may require additional supports alongside the CICO intervention to prevent or reduce the challenging behaviors. This article describes how to implement CICO, providing examples from one childcare center's successful experience with a 3-year-old student.