Gerling has been put up for sale after shareholder Deutsche Bank persuaded the founder's grandson, Dr Rolf Gerling, to sell his 65.5% share, according to reports.
Deutsche Bank has a minority share in the group.
The move was made because no companies were interested in a minority share alongside Gerling.
A statement from Gerling said both parties "have agreed on finding a strategic partner to guarantee the long-term development of the group".
The new partner would hold the majority of the Gerling shareholding.
A joint shareholder committee would be in charge of finding the new partner, the statement added.
Gerling Group of Insurance Companies is the fourth largest insurer in Germany with a premium volume of €10.4bn (£6.44bn) in 2001.
It employs 13,000 staff and is the second largest credit insurer and the sixth largest reinsurer worldwide.
