Abstract Introduction: Use of progressive technology, clinical skills and caring methods appropriate to critical situations of patient in intensive Cardiac Care Unit is probably related to professional errors and disorder in patient safety. There is a little data about this subject. Objective: The aim of this study was to explore professional errors and patient safety in Cardiac Care Unit. Methods: This study was conducted using qualitative approach and conventional content analysis method. Fifteen Cardiac Care Unit nurses participated in this study during 2012-2013. Samples were selected purposefully and data collection method was through semi-structured interview. Results: Data analysis of extracted contexts, the main theme abstracted was "teamwork". Subthemes included "empowerment", "job satisfaction" and "supporting management". Conclusions: Study results indicated that providing teamwork is very important in reducing errors, maintaining and improving patient safety in Cardiac Care Unit. Also necessity of supporting management regarding suitable confrontation with error, empowerment and increasing nursing job satisfaction are basic principles of professional error prevention and provision of patient safety.