"We must assume at this point that two German citizens were kidnapped Sunday night in southern Nigeria, in the Niger Delta," foreign ministry spokesman Andreas Peschke told a government news conference.
"The foreign ministry and our experts on the ground are in contact with the responsible authorities in Nigeria. We are trying everything possible, with these authorities, to resolve this case as soon as possible."
He declined to provide further details in the interest of the hostages' safety.
A security source in Lagos said the two German men, aged 45 and 55, were kidnapped Sunday after an outing at a beach in oil-producing Abia State in the southeast of the country.
One works in Port Harcourt, the capital of Rivers State, while the other came from Nigeria's commercial capital of Lagos, the source said.
No group has claimed responsibility for the kidnapping.
Hundreds of foreigners and locals, mostly oil workers - have been kidnapped since 2006 in Nigeria, mostly in the oil-rich Niger Delta.
Many have been released unharmed, but some only after ransom payments.