The Purpose of this Research is to Investigate the Principles of Professional Ethics of Accountants In Relation to the Transparency of Financial Information. This Research is Applied and Correlation Research. The Statistical Population of the Research Included Managers, Experts and Accountants of Companies Based in Tehran, and 35 Companies were Randomly Selected as a Sample. The Data Collection tool Includes a Researcher-Made Questionnaire, the Validity of Which is Measured by the Professors and the Reliability of the Tool Through Cronbach's Alpha. Data Analysis has Been Done Through Descriptive and Inferential Statistical Methods. The Results of the Research Show that there is a Positive and Significant Relationship Between the Principles of Professional Ethics (Including Honesty and Integrity, Independence and Impartiality, Confidentiality and Social Responsibility) and the Transparency of Financial Information. Ethics is a Common and Necessary Topic in all Active Professions in the World; Because if there is Professional Ethics in a Profession, that Profession Will Progress, Otherwise one Should Wait for the Destruction of that Profession.