This study aims to develop a valid and reliable inventory of the teaching profession’s ethical principles. With this aim, a list of ethical principles has been formed first from inventories, scales, and questionnaires located in the literature then from ethical codes currently in use. Afterwards, an interview was held with a group of teachers (n = 15) who had been selected using the convenience sampling method so as to identify the issues that teachers view as ethical problems and to be able to understand their points of view in depth. The results of the content analysis performed on this interview data have been drafted and added to the ethical principles list that was formed. A focus-group interview was held with teachers (n = 14) who had been chosen using critical sampling, a purposeful sampling method, for the purpose of identifying the items they wanted to add/subtract related to the 125-item list of principles prepared from the literature search and interviews and the purpose of being able to learn their ideas and comment about these items. The draft version of the Teaching-Profession Ethical Principles Inventory was formed in this way. The draft was ap- plied to 305 teachers chosen from teachers working in a provincial center of Turkey’s Aegean region using the multi-stage cluster-sampling method, and validity and reliability analyses were conducted over the data. As a result of the performed exploratory factor analysis, the KMO coefficient of sampling adequacy was found to be .91, and Bartlett’s sphericity test was found to be significant at p < .001. As a result of analyzing the basic-components, the inventory has been determined to have a six-factor structure, and these factors explain 49.99% of the total variance. Cronbach’s alpha of internal reliability was found between .51 and .91.