The embassy said in an emergency message that the target of attacks would be hotels frequented by Westerners in the capital of Abuja.
The embassy said the Nigerian government is aware of the threat and is implementing additional security measures.
"Please maintain a high state of vigilance and personal security awareness," the emergency message said.
It went on to advise Americans to monitor local news stations for updates and report specific incidents of targeted violence to the U.S. Embassy in Abuja.
Boko Haram has killed hundreds of people in gun and bomb attacks this year to push for the adoption of Shariah law in the African nation.