The early childhood field is increasingly beginning to recognize the importance of integrating science, technology, engineering, arts, and mathematical concepts into preschool classrooms. Despite this recognition, preschool teachers often face challenges integrating these subjects due to insufficient knowledge, training, and resources. This qualitative single case study sought to understand the role of in-service training in preschool teachers' knowledge and perceptions regarding intentional teaching practices for integrating subject areas in their classrooms while utilizing the framework for intentional teaching as the conceptual underlying support. Eleven preschool teachers participated in the study and underwent a 6-hour in-service training focused on intentionally integrating science, technology, engineering, arts, and mathematical concepts into their preschool classrooms. Data for the study was collected through pre- and post-interviews, pre- and post-observations, and notes taken from discussions during training sessions. A thematic analysis was used to identify patterns in teachers' views on integrating science, technology, engineering, arts, and mathematics concepts in their teaching. The findings showed a growing understanding of the relevance and importance of integrating these concepts. The research findings suggest that when teachers purposefully incorporate these concepts, they can provide more meaningful learning experiences. The integration of these concepts can support the scaffolding of children's learning, by promoting a deeper understanding of knowledge. However, a considerable gap exists in the availability of these types of training opportunities for preschool teachers. One of the most significant barriers to the integration of these concepts is the lack of accessible materials and resources. A recommendation for future research is to examine the long-term effects of intentionally integrating science, technology, engineering, arts, and mathematical concepts in lessons and activities with limited materials and resources. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]