The current study was undertaken with the purpose of developing and validating a willingness to communicate (WTC) questionnaire for instructional language teaching and learning contexts. Six instructional WTC (IWTC) components were identified after (1) undertaking a comprehensive review of the literature on second language (L2) WTC and other L2-related personality and situational factors, such as language anxiety, communication apprehension, language attitude, self-confidence, introversion/extroversion, motivation, learner identity and class dynamism and (2) conducting interviews with domain experts and language teachers. The six IWTC components included communicative self-confidence, integrative orientation, situational context of L2 use, topical enticement, learning responsibility, and off-instruction communication. Then, a draft version of an IWTC questionnaire consisting of 42 items was first piloted with 218 Iranian English-as-a-Foreign-Language (EFL) learners and the obtained data were submitted to exploratory factor analysis. The results showed that the questionnaire consists of a clear six-factor structure. The subsequent confirmatory factor analysis of the data from another 624 Iranian EFL learners indicated that the six-factor structure of the questionnaire can be statistically supported, meaning that the questionnaire's detected factor structure was not the result of random variance in the learners' responses.