The Russian news agency RIA said the deal was signed during the recent visit of South Ossetia's foreign minister to Nauru which marked its 50th anniversary of independence.
Nauru has the region's tightest visa policy and apart from several South Pacific countries, it only allows visa-free access to citizens from four countries - Israel, Taiwan, the United Arab Emirates and Russia.
In addition, it charges $US6000 as a non-refundable fee for visa applications if they are filed by journalists.
Nauru is also one of only four countries recognising South Ossetia as an independent country.
It has also recognised another Georgian break-away region, Abkhazia, as a separate country.