Background: Unilateral anisocoria has a variety of causes, some of which could be life-threatening. Mydriasis can represent a serious neurological finding in intensive care units. Bronchiolitis is the most common cause of intensive care in the infancy period. Ipratropium bromide is anticholinergic and commonly used in the intensive care unit (ICU). Anisocoria is due to the overactivation of the sympathetic nervous system or hypoactivity of the parasympathetic nervous system. Objectives: Assessment of cases of anisocoria in infants with bronchiolitis under ipratropium bromide therapy. Patient and methods: A case report study of a 9-month-old infant with a fixed dilated pupil. He was admitted into the ICU and given ipratropium bromide. Results: Ultimately, the patient's symptoms of pupillary dilation resolved over 24 hours with the discontinuation of ipratropium bromide, with a complete recovery. The case presented here is typical of anticholinergic side effects, and the evidence of this benefit is even more limited, which might lead to frustrating observations among patients and health care providers. Conclusion: Anisocoria is not an uncommon finding in patients receiving ipratropium bromide. Paediatricians should follow the Saudi Bronchiolitis Guideline recently published in 2018, in which no indication of ipratropium bromide in bronchiolitis was clearly stated.