AFib is usually accompanied by symptoms related to a rapid heart rate and the loss of synchrony between the atria and ventricles. Rapid and irregular heart rates may be perceived as palpitations, exercise intolerance, and occasionally produce angina (if the rate is faster and puts the heart under strain) and congestive symptoms of shortness of breath or edema. Sometimes the arrhythmia will be identified only with the onset of a stroke or a transient ischemic attack (TIA). It is not uncommon for a patient to first become aware of AF from a routine physical examination or ECG, as it may be asymptomatic in many cases.

• Heart palpitations - Sudden pounding, fluttering or racing sensation in the chest
• Lack of energy or feeling over-tired
• Dizziness - Feeling lightheaded or faint
• Chest discomfort - Pain, pressure, or discomfort in the chest
• Shortness of breath - Having difficulty breathing during normal activities or even at rest.
• Leg swelling - due to heart failure
• Nocturnal dyspnea - Worsening shortness of breath at night.
• Weight gain - due to fluid overload from heart failure
• Fatigue - Feeling tired and out of energy

As most cases of atrial fibrillation are secondary to other medical problems, the presence of chest pain or angina, symptoms of hyperthyroidism (an overactive thyroid gland) such as weight loss and diarrhea, and symptoms suggestive of lung disease would indicate an underlying cause. A previous history of stroke or TIA, as well as hypertension (high blood pressure), diabetes, heart failure and rheumatic fever, may indicate whether someone with AF is at a higher risk of complications.