This qualitative embedded single case study explored the teacher competencies and instructional strategies used in classroom one-to-one implementations. The specific problem was that school administrators have spent significant amounts on one-to-one technology without substantial change in teacher practices, causing limited benefits to students from these investments. The purpose of this study was to describe the teacher competencies and instructional strategies used in classroom implementations that positively affect the success of a district-wide one-to-one technology adoption from the principals', teachers', and technologists' perspectives. Twenty-two participants including teachers, principals, and instructional technologists from one urban school district in Illinois provided information through semi-structured interviews. Teachers also completed a modified Technological Pedagogical Content Knowledge (TPACK) survey. Guiding this study were three research questions, three sub-research questions, and the TPACK framework developed by Koehler and Mishra. Koehler and Mishra indicated that there are specific competencies that teachers must possess to successfully integrate technology into their classrooms. Among all participant groups, eight primary and 23 subthemes were revealed. Three themes and five subthemes were referenced in multiple participant groups. These themes were "Active Learning Strategies," "Technological Knowledge," and "Content Knowledge." The subthemes referenced by multiple groups were "Google Suite," "Interactive Whiteboards," "Learning from Students," "Technology Department Support," and "Collaboration with Colleagues." Study findings suggest that the study district should redesign their existing professional development system, treating each classroom, teacher, and principal as if this is the beginning of their one-to-one implementation. A sequential professional development program should be developed and provided in a required manner. Additional quantitative research is also suggested. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]