Although research has demonstrated that introducing computational thinking (CT) benefits young children, there has been a lack of systematic professional development (PD) opportunities for preschool teachers. The current study investigated the impact of Teaching through Interaction-Plus (TTI-P) on preschool teachers' self-efficacy in teaching CT to preschool children, which focuses on high-quality teacher-child interaction. A quasi-experimental design was used to train 23 in-service preschool teachers and 111 children in the TTI-P program for 15 weeks. A control group consisting of six teachers and 75 children was also included. The results showed that the TTI-P training effectively increased preschool teachers' self-efficacy in teaching CT. Additionally, children in the experimental group showed better CT skills than those in the control group. Based on findings from the current study, we offer implications for supporting preschool teachers with high-quality interaction that promotes critical thinking and problem-solving skills during CT activities.