This study reports on the development of a self-reported measurement instrument--The Teacher Educators' Researcherly Disposition Scale (TERDS)--to improve understanding of teacher educators' researcherly disposition. Teacher educators' researcherly disposition refers to the habit of mind to engage with research--both as consumers and producers--to improve their practice and contribute to the knowledge base on teacher education. Taking into account the shortcomings of the emerging field of teacher educator professional development research (which is largely confined to small-scale, qualitative studies), a large-scale quantitative survey study (n?=?944) was conducted. The first part of the article reports the results of factor analysis (EFA and CFA), which suggest a four-factor structure of teacher educators' researcherly disposition: (1) "valuing research" (a?=?0.86), (2) "being a smart consumer of research" (a?=?0.89), (3) "being able to conduct research" (a?=?0.82), and (4) "conducting research" (a?=?0.87). Goodness of fit estimates were calculated, indicating good fit. The second part of the article explores differences in teacher educators' researcherly disposition across several subgroups of teacher educators using the developed instrument. Results indicate that having research experience leads to significantly higher scores on each of the subscales. Furthermore, significantly higher scores were found for those with more than 3 years' experience as a teacher educator, as well as for those without (prior) teaching experience in compulsory education. To conclude, the implications for further research and practices related to teacher educators' professional development are discussed.