Asthma is one of the most common chronic illnesses in children. Children with asthma often suffer from night coughing, wheezing and breathlessness that disturb their sleep. Nocturnal asthma is often associated with such problems as difficulty falling asleep, restless sleep, difficulty maintaining sleep, daytime sleepiness, and daytime tiredness. These sleep problems not only occur in children but also in their parents, and furthermore affect their daytime activity. People with asthma should be aware that nocturnal asthma is associated with more severe symptoms and increased mortality. Several underlying mechanisms that may shed light on how and why nighttime seems to exacerbate asthma symptoms include the inflammation process, airway resistance, and bronchial hyper-responsiveness (all circadian factors) as well as gastro-esophageal reflux (a non-circadian factor). Nurses should understand the mechanisms of nocturnal asthma and conduct sleep assessments comprehensively in order to design and implement appropriate strategies to improve the sleep quality of children with asthma.