Although studies investigating online learning and teaching have proliferated recently, one area that has been underexplored is foreign language teachers’ readiness to incorporate the flipped classroom into their repertoire at the K-12 level. Accordingly, the present study aims to provide an instrument to assess K-12 foreign language teachers’ teaching readiness to flip their classes. The study draws on data from 489 pre-service and in-service K-12-level foreign language teachers using an online platform during the fall of 2022. Results of exploratory factor analysis (EFA) and first- and second-order confirmatory factor analysis (CFA) were attained via responses to a 20-item questionnaire comprising seven dimensions: technological content knowledge (TCK), technological pedagogical knowledge (TPK), and technological pedagogical content knowledge (TPCK), perceived usefulness (PU), perceived ease of use (PEU), attitude (A), and behavioral intention (BI). Findings revealed that the newly developed instrument measuring teachers’ readiness to flip their classes is valid and reliable. Researchers and teacher educators may use this scale to gain a greater understanding of K-12 foreign language teachers’ readiness for flipped teaching with domain-specific items.