There is growing attention for integrating Computational Thinking (CT) into various subjects across the K-12 curriculum with a concomitant increase of interest in investigating teachers’ pedagogical content knowledge (PCK) regarding CT. This study is part of a bigger project focusing on defining the learning trajectories for CT integration into the K-12 curriculum. In particular, the present study focused on eliciting the pedagogical content knowledge and attitude of teachers with respect to the integration of CT in various disciplines. To this end, we implemented six different case studies by integrating CT into six different subjects: science, traffic, language, biology, geography, and physics. Two primary and four secondary school teachers were involved in the study. After the lesson series was completed in schools, we conducted interviews with teachers to understand their PCK on CT integration, attitudes toward CT integrated lessons, and the barriers teachers faced during CT integrated lessons. Our results indicate that compared to standard instructional activities, students can go deeper and understand the subject content better in CT integrated lessons, also students can use the power of digital technologies to solve subject-related problems. On the other hand, teachers pointed out that students and teachers need to be more capable of technical knowledge and skills to accomplish tasks.