<p>Teachers’ mental health problems have been shown to adversely affect their subjective well-being as well as students’ emotional health and learning. A person’s stress mindset has an important influence on their mental health. However, the mechanism through which stress mindset affects teachers’ mental health remains unclear. Drawing on stress mindset theory and scarcity theory, we propose time poverty as a mediator. We conduct a two-wave longitudinal study, with primary and secondary school teachers as participants (<i>N</i> = 322), to investigating the association between stress mindset (Time 1), time poverty (Time 2), and mental health issues (including anxiety, stress, and depression) (Time 2). The results indicate that (1) stress mindset directly and negatively predicts teachers’ mental health; (2) stress mindset significantly and negatively predicts time poverty, and time poverty significantly and positively predicts teachers’ mental health issues; and (3) the time poverty of teachers mediates the correlation between their stress mindset and mental health issues of all types (including depression, anxiety, and stress). The study enriches both scarcity theory and stress mindset theory and suggests a promising pathway for safeguarding teachers’ mental health.</p>