This article describes a professional development (PD) model, the CT-Integration Cycle, that supports teachers in learning to integrate computational thinking (CT) and computer science principles into their middle school science and STEM instruction. The PD model outlined here includes collaborative design (codesign; Voogt et al., 2015) of curricular units aligned with the Next Generation Science Standards (NGSS) that use programmable sensors. Specifically, teachers can develop or modify curricular materials to ensure a focus on coherent, student-driven instruction through the investigation of scientific phenomena that are relevant to students and integrate CT and sensor technology. Teachers can implement these storylines and collaboratively reflect on their instructional practices and student learning. Throughout this process, teachers may develop expertise in CT-integrated science instruction as they plan and use instructional practices aligned with the NGSS and foreground CT. This paper describes an examination of a group of five middle school teachers' experiences during one iteration of the CT-Integration Cycle, including their learning, planning, implementation, and reflection on a unit they codesigned. Throughout their participation in the PD, the teachers expanded their capacity to engage deeply with CT practices and thoughtfully facilitated a CT-integrated unit with their students.