Introduction: The goal of professional librarians and informatics is providing useful services for users. This study aims to recognize the rate of commitment and authority of librarians to ethics instruction.

Method: this study is an applied ex post facto research. The population of study includes all librarians of Isfahan public libraries in 2012. By in access selection, 207 questionnaires were filled by participants. The questionnaire was made by authors. Data were analyzed by descriptive and inferred statistics.

Results: The findings showed that librarians are familiar and committed to ethical principles, but they don’t use these instructions in their duties. Experience has significant effect on theoretical ethics but not on applying ethics in work. Gender, age and education have no significant effect on professional ethics.

Conclusion: It can be said that most of librarians were familiar with professional ethics instructions, but they don’t apply this instructions. Therefore, unannounced inspections are necessary.