Background: The aim of this study is to identify the sociodemographic characteristics and the most frequent diseases and nursing interventions carried out on migrants arriving by sea at southern Spain. Method: Cross-sectional, descriptive, and retrospective study based on the database of the Spanish Red Cross Intervention Activation System. All migrants who arrived on the coasts of a southern province during 2016 and were assisted by the Red Cross were included. Results: A total of 2027 people were registered, mostly males, aged between 18 and 40 years. Of these, 4.9% required healthcare, and 2.9% were referred to hospital. Highlighted diagnoses were headaches (15.6%), pregnancy (12.8%), and lower-limb wounds (6.4%), and outstanding nursing interventions were “care of wounds” (24.7%), “pain management” (21.9%), and “prenatal care” (15.2%). Statistically significant relationships were found between the diagnosed diseases and gender, geographic area of origin, and seasonal time of the year, as well as between nursing interventions performed and those three variables. Conclusions: Although in general, a good health condition was observed in most of the migrants treated, the most frequent health situations attended were related to dermatological, gynecological, and headache problems. The most performed nursing interventions were related to skin/wound care and promotion of physical comfort, requiring a low need for hospital transfers. Female gender, origin from sub-Saharan Africa and arrival in the summer period carry a greater risk of suffering health problems when migrants reach Spanish coasts.