American oil giant Exxon Mobil said the hostages, four Britons, an Indonesian, a Malayasian and a Romanian, were freed in good health.
The men were captured when gunmen burst into a bar inside the Exxon compound at Eket, killing several Nigerian security guards.
The men's employer said he would not be giving details of communications with the group who captured the men and police said they had no details of the terms of their release.
Hostage-taking has become a lucrative business for armed groups in the Niger Delta.