You must obtain your visa before you travel to Nauru; there is no visa issuance on arrival. To enter Nauru, you need:
a valid passport with a minimum of three months validity
an onward/return ticket
proof of hotel bookings (or sponsorship from a resident of Nauru)
For more information on entry/exit requirements, you may wish to contact Republic of Nauru Permanent Mission to the United Nations in New York at 212-937-0074 or by fax at 212-937-0079. The address is: 800 Second Avenue, Suite 400A New York, NY 10017.