Nomophobia is the fear of leaving the house without a mobile and being out of mobile phone contact and affects different areas of a person's life, especially in terms of social, work and academic relationships due to a dependence on the use of smartphones. Discovering the prevalence of nomophobia among nursing students is very important, as the misuse of smartphones in clinical practice may cause distractions, affecting the quality of care and putting patient safety at risk. Furthermore, it can lead to poorer academic performance during class. The aim of this study was to compare the levels of nomophobia experienced by nursing students at the University of Almeria, Spain and the Polytechnic Institute of Braganza, Portugal. A comparative descriptive observational study was carried out. A nomophobia questionnaire adapted to the Spanish and Portuguese sociolinguistic context was employed; 258 participants comprised the subjects of study. The main results showed both Spanish and Portuguese nursing students scored higher than average regarding levels of nomophobia. However, the scores gathered from items on the questionnaire were generally higher among the Portuguese population than the Spanish one. The Portuguese students (54.7%) felt more anxious than the Spanish students (35.4%) if their battery ran out. Similarly, the Portuguese population showed a greater need for instant communication with their family and friends. In conclusion, the dimensions explored indicate significant levels of nomophobia among both nursing student populations, with higher levels among the Portuguese population than the Spanish.