With rapid development of emerging technologies, teachers have been required to integrate mobile technology into their practices to improve learning outcomes. However, teachers have been reluctant to integrate technology into teaching because of technostress. Many studies have investigated the reasons and consequences of technostress in different contexts more than education, specifically teachers in K-12. To shed light on the boundary condition of using new technology, this study investigated technostress as a boundary condition that influences perceived usefulness for continuance intentions of using portable technology. Therefore, the authors introduced a model to describe the relationship among technostress, perceived usefulness, and K-12 teacher attitudes toward and continuance intentions to using mobile technology in the Palestinian context. 367 teachers from different backgrounds participated in the quantitative study. SPSS and AMOS were used to find the path coefficients of the model. The findings revealed that technostress has non-significant direct effects on continuance intentions of using portable technology, where perceived usefulness plays a crucial role in continuance intentions. Technostress has negative effects on both perceived usefulness and teachers' attitudes toward mobile technology. Participants in the study were from northern Palestine, which limited generalizing the findings on other technological tools. Longitudinal future studies are recommended to understand the impact of perceived usefulness and its relationship with technostress, which is important to deepening our understanding of continuance intentions in using mobile technology.