Aims and objectives. To explore illness beliefs in couples where one spouse has atrial fibrillation.& para;& para;Background. Beliefs are the lenses through which we view the world, guiding our behaviour and constructing our lives. Couples evolve an ecology of beliefs from their interaction whereby their actions and choices arise from their beliefs. Atrial fibrillation is a common cardiac arrhythmia that has implications for both patients and partners. A couple's illness beliefs play an important role in convalescence and illness management, and no previous studies have explored illness beliefs in couples living with atrial fibrillation.& para;& para;Design. A qualitative hermeneutic design.& para;& para;Methods. Data collection constituted in-depth interviews with nine couples (patient and partner together). Hermeneutic philosophy as described by Gadamer was used to interpret and to understand illness beliefs in couples living with atrial fibrillation.& para;& para;Results. The findings revealed both core illness beliefs and secondary illness beliefs. From the core illness belief 'The heart is a representation of life', two secondary illness beliefs were derived: atrial fibrillation is a threat to life and atrial fibrillation can and must be explained. From the core illness belief 'Change is an integral part of life', two secondary illness beliefs were derived: atrial fibrillation is a disruption in our lives and atrial fibrillation will not interfere with our lives. Finally, from the core illness belief 'Adaptation is fundamental in life', two secondary illness beliefs were derived: atrial fibrillation entails adjustment in daily life and atrial fibrillation entails confidence in and adherence to professional care.& para;& para;Conclusion. Couples' interaction has developed mutual illness beliefs regarding atrial fibrillation that guide them in their daily lives and influence their decisions. The adoption of a family-centred perspective in cardiovascular care settings is warranted.