Beliefs, attitudes and anxiety levels of schoolteachers are important factors influencing the acceptance, adoption and integration of mobile devices in teaching. To understand how to sustain device use, we need to understand what influences teachers and how such factors can change. We adopted a quasi-experimental design using pre- and post-questionnaires to investigate factors influencing the beliefs, attitudes and anxiety levels of teachers before and after using such devices to teach different subjects. Sixty-two secondary school teachers were divided into two groups--language and humanities, and mathematics and science. Repeated measures ANOVAs were used to analyze questionnaire data, and showed the mathematics and science group experienced a positive change in beliefs after use of mobile devices, but the language and humanities group did not. Both groups experienced lower levels of anxiety, but unchanged attitudes, after device use. Implications for teacher professional programs, school policies and ongoing support for mobile device integration are discussed.