Teaching is a stressful profession with a high turnover rate. Schools and related institutions need to take more action to support teachers and keep teacher stress at a manageable level. The continued research and practical effort require measures to examine teachers' stress in a briefer and accurate manner. The Teacher Stress Scale is a recently developed brief measure to examine teacher stress with promising psychometric characteristics. The present study aims to further validate TSS scores with a large sample of teachers ranging from pre-kindergarten to the 12th grade from the United States and United Kingdom. Findings of the internal structure validity, convergent validity, and the internal consistency reliability of TSS scores were examined. Specifically, the confirmatory factor analysis of the unidimensional model and the two-dimensional model showed poor fit, but the bi-factor model evidenced a strong fit. Factorial invariance testing yielded strong invariance between early education and secondary education teachers as well as satisfactory invariance between teachers from the United States and the United Kingdoms. The Inadequate School-Based Support TSS subscale demonstrated convergent validity with other support measures, and the overall TSS showed acceptable internal consistency reliability evidence of scores. Limitations and implications of the TSS, as well as future research directions were discussed.