Young children are perfectly adapted to learning STEM concepts. A growing body of research indicates that experiences with science, Technology, Engineering, and Mathematics (STEM) are critical in preparing young children to think critically and creatively and solve problems. These are valuable skills young children need to succeed in school, work, and life. This raising awareness of STEM education needs has pushed for STEM integration in early childhood (EC) settings while giving limited attention to the teaching of STEM in the EC field and targeted STEM professional development programs. This qualitative study aimed to explore the EC teachers' pedagogical beliefs and practices about STEM-integrated curriculums and STEM teaching in pre-K settings after attending a series of STEM integration teacher professional development programs in an eastern state in the United States. Five EC teachers participated in in-person interviews after attending a series of professional development sessions designed to help teachers develop both content knowledge and pedagogical knowledge related to the STEM curriculum. A qualitative inductive approach was used for the data analysis. The analysis of data collected from interviews with EC teachers revealed that they were positively impacted by the STEM-integrated professional development, resources, and materials available to implement the STEM units. According to the teachers' beliefs, children were also positively impacted by their teacher's professional learning and high confidence in teaching STEM-related topics and activities. A discussion of the findings and implications for future research and practice is presented. Recommendations are also discussed for how teachers can effectively teach integrated STEM education.