To enter, citizens of all Western countries need a visa. West African passport holders do not need a visa.
Mauritania visas for 0-30 days are available on arrival for 120 Euros as of August 2015. Overland travelers may get them in Rabat, for example, where a single entrance visa costs 1000 MAD. For 1100 MAD, a double-entry visa is also available. Two passport-size photographs, as well as a copy of your passport’s information pages, are needed. For most nations, visas are available the same day in the afternoon if applied for in the morning.
In Mauritania, immunizations are not needed for the majority of the population. Only those traveling from areas where yellow fever is prevalent are needed to provide proof of immunization.