Background The study aimed to develop a reliable and valid Teachers’ Body Posture Literacy Questionnaire (TBPLQ) to examine their body posture knowledge. Methods The tool was based on a Parents Body Posture Literacy Questionnaire (PBPLQ) and modified and validated through discussion with experts, conducted in two rounds. Corrective gymnastics, physiotherapy, ergonomics, and physical education (PE) experts and doctoral and postdoctoral scholars evaluated content validity. Test-retest repeatability was tested using Cohen’s kappa coefficient. The study used a convenience sample of 195 teachers from three different educational levels: PE, kindergarten, and primary education in two rounds of test-retest (pilot test-retest reliability and main test-retest reliability of the questionnaire). The first round encompassed 95 participants, with pre-test and post-test procedures applied using the original TBPLQ. The second round involved 100 participants and followed a similar approach, incorporating modifications to the TBPLQ based on the reliability outcomes observed in the first round. Results The results of the first-round test-retest TBPLQ reliability, with 95 samples, resulted in an overall reliability of 0.77 (range 0.02 to 1). This indicated that the questionnaire still lacks sufficient reliability. Consequently, after the necessary amendments and modifications, the questionnaire’s reliability was tested for the second time with 100 samples. Notably, the overall reliability of 0.82 (ranging from 0.50 to 1) was established for the TBPLQ indicating that 87.5% of the questionnaire items achieved reliability scores within the substantial and almost perfect range and only 12.5% of the items attained moderate reliability scores. Conclusions The questionnaire is a new self-report measure for evaluating teachers’ literacy in postural health. It is applicable in both research and practical contexts, extending its use to larger and more diverse populations.