This study examined the stability and change patterns among toddlers’ interactions with their teachers, teachers’ sensitivity, and toddlers’ development during the COVID-19 pandemic and the three plausible paths were tested to identify which of the study variables affected the developmental trajectories in toddlers over time. Sixty- three toddlers and six head teachers from a childcare center in Korea were sampled. The data on toddler-teacher interaction and teachers’ sensitivity were collected by observation during free play using a camera, and the toddler’s temperament and development were assessed by his or her mother. Toddlers who had been actively involved in initiating their verbal interactions with teachers showed more verbal interactions with their teachers even after 4 months passed. Also, the study found that the early (T1) social disposition of toddlers and the behavioral interaction that toddlers had initiated with teachers revealed each of the simultaneous, cumulative, and complex effects. These results support the contention that the nature of interactions vary by contexts of subject, time, and socio-history, and new competencies should be required for teachers within the multi-faceted pandemic and its ramifications on toddler development.