Test results have confirmed several cases of the H5N1 virus, said the World Organisation for Animal Health (OIE).
Niger, one of the world's poorest countries, has a long border with Nigeria, where bird flu has killed thousands of chickens.
No human cases of the H5N1 strain have yet been found in Africa but the UN has warned of a possible regional disaster.
The H5N1 strain was found in domestic ducks near Nigeria's border, the OIE said.
"We've been officially informed that the presence of the virus has been notified on the sample from Niger but we are waiting for official documents to know... what type of strain it is," said Niger's government spokesman Mohamed Ben Omar.
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