Background: Atrial Fibrillation (AF) is the most broadly recognized managed arrhythmia around the world. Identified knowledge and self-care to patients with AF is the way to successfully live with their disease. So necessary to this knowledge to be identified. This study aimedto assess knowledges and self-care of patients recently diagnosed with atrial fibrillation. A descriptive design was used in the current study. The study was conducted at intensive care unit and Cardiac care unit in El- zohor hospital, Port Said general hospital and El-tadamon hospital at Port Said city. A convenience sample of 110 patients recently diagnosed with atrial fibrillation included in this study. Tools of data collection, two tools were used for data collection; Patient's knowledge relevant information questionnaire and Patient's Self-care Scale. Results of the study revealed that, most of patients had moderate knowledges about atrial fibrillation and the level of self-care was observed to be high in male, highly percent among educated patients, in the individuals who work and live in urban areas. Knowledges was positive predictor of AF and self-care practice. Conclusion: most of studied patients had unsatisfactory knowledges and self-care about atrial fibrillation regarding themselves. The current study recommended that, Well-planned orientation, in-services training program and proper supervision of patients with atrial fibrillation is recommended