Building on theoretical and empirical insights and applying the thriving theory as the conceptual framework, the authors developed two new teacher-specific scales, namely the Teacher Stress Scale and the Teacher Thriving Scale. The goal of this investigation was to evaluate the psychometric properties of these two scales. Data were collected through an online questionnaire administered to a national sample of 122 participating early childhood teachers teaching in preschool through third grade in 26 states of the United States during the 2020–2021 (...) school year amidst COVID-19. This study revealed some important psychometric results. First, with respect to their internal structures, both the TSS and the TTS appeared to be best represented as bifactorial and trifactorial, respectively. Specifically, the TSS comprised two constructs: Inadequate School-based Support, and Teaching-related Demands; and the TTS encompassed three constructs: Adaptability and Flexibility, Personal Strengths and Professional Growth, and Positive Mindset. Second, the negative correlation between the TSS and the TTS provided discriminant evidence for each other’s construct validity, while the positive correlations between the TTS and six conceptually cognate constructs demonstrated convergent evidence for construct validity for the TTS. Third, both the overall TSS and the overall TTS as well as their subscales exhibited good internal consistency reliability. Fourth, both the overall TSS and the overall TTS also demonstrated test–retest reliability. (shrink)