Grey said it plans to raise approximately $100m (£59.7m) through a private offering and may raise up to an additional $25m.
In a statement, Grey said it expects to use the cash for working capital and other general corporate purposes, which may include "without limitation, possible acquisitions".
Grey was earlier this year linked to one of the possible bids vying for Cordiant Communications, which eventually fell to WPP Group. However, other than that the group has seen little activity on the acquisition front.
Grey, which owns the Grey Worldwide advertising network, said it had no specific agreements or commitments, and was not currently engaged in any acquisition talks.
Grey is the world's seventh largest advertising group, but along with sixth-placed Havas it lags behind rivals Omnicom, Interpublic and WPP Group.
Last week, Grey chairman and CEO Ed Meyer hit back at comments made by Sir Martin Sorrell, who derided the future prospects of the mid-sized advertising holding groups.
"The view of some of my counterparts that the size of the holding company is the only thing that matters is totally silly. I have no quarrels with the megas. Some will do well and some will explode because they're a management nightmare," Meyer said.
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