Background: Professional nursing organizations recommend the use of nursing diagnosis to enhance and facilitate the standardization of care and the development of a common language used by nursing practitioners. In the clinical reality of hospital emergency departments, however, its use is controversial. The objectives of the research are (a) to explore the use of nursing diagnosis in hospital emergency departments, and (b) to describe the meaning of nursing diagnosis for hospital emergency nurses. Methods: A qualitative phenomenological study was conducted. A purposeful sampling and snowball technique were used. Data were collected using in-depth interviews, researchers` field notes, and documental analysis. An inductive analysis based on Giorgi´s proposal was used to identify significant emerging themes from interviews and field notes. Seventeen participants with a mean age of 40 were recruited. Results: Three themes were identified. The results showed how the use of nursing diagnosis in hospital emergency departments depends on nurses to apply a working methodology in their practice, along with other dimensions such as the characteristics of emergency care, the type of health problems, and the complexity of care. Conclusions: The use of standardized language in emergency departments is complex due to the overcrowded nature of care in these settings.