Sleep related breathing disorders are common as well as a poor prognostic sign associated with higher mortality in patients with congestive heart failure (CHF). These patients often have a shorter total duration of sleep, disturbed sleep structure and increased daytime sleepiness, which can negatively affect all dimensions of the life situation. The spouse has an important role in supporting the patient in relation to sleep disorders, but this role may be adversely affected by the sleep situation of the couple. The aim of this study was to describe decisive situations that influence spouses' support to patients with CHF in relation to the couple's sleep situation. A qualitative descriptive design using critical incident technique was employed. Incidents were collected by means of interviews with 25 spouses of patients with CHF, strategically selected from two hospital-based specialist clinics in southern Sweden. Two main areas emerged in the analysis: support stimulating situations and support inhibiting situations. Support stimulating situations described how spouses' support was positively affected by their own adaptation in psychosocial or practical situations, and receiving help from others. Support inhibiting situations described how the spouses' support was negatively affected by sleep disturbances as a result of the patient's symptoms, anxiety in relation to the disease, limitations as a result of the sleeping habits, dissatisfaction with care related to the sleep situation, and being left to cope alone with the problems. An increased understanding of the stimulating and inhibiting situations influencing spouses' support for patients with CHF can guide health care personnel in deciding if an intervention is needed to improve the sleep situation for patient and spouse.