The parties are understood to be in due diligence, although final terms, including price and earn-out details, have yet to be agreed.
Dare, one of the largest remaining creative independents in UK digital marketing, has been the subject of various bids from interested suitors, including Publicis, in recent months.
The agency was founded in 2000 by Mark Collier, a founding partner of Bartle Bogle Hegarty. Ownership of the majority of shares is currently split between Collier, planning partner John Owen and creative partner Flo Heiss as well as other agency staff.
BBH holds a minority stake, understood to be in the region of 30 per cent, which it bought in 2002. This year, BBH set up its own digital arm after winning the European digital account for Lynx, which was previously split between Dare and AKQA.
Cossette is best known in UK advertising for its 2005 acquisition of Miles Calcraft Briginshaw Duffy. The group paid an initial £7.8 million for a 51 per cent stake in the agency, rising to a potential £27 million as part of a six-year earnout.
Cossette favours deals that allow businesses to maintain their autonomy and encourages founders to stay with their agencies through long earnout arrangements.
As well as MCBD, Cossette owns the PR agency Band & Brown, the design shop Identica and the direct marketing group Elvis. It operates in North America and across Europe.
Dare, which has been named Campaign's digital agency of the year three times, is one of the only UK digital specialists to remain up for grabs. Others include the media agency i-level, which has set up its own holding company, the full-service agency Profero and the creative agency Grand Union.
Collier declined to comment. Cossette did not respond to calls.