The deal is expected to close in Q4 2013 at the latest, subject to regulatory approvals.
Earlier this year, Hartwall (circa. €300m sales in 2012) launched the EU's first stevia-sweetened alcoholic drink, and has strong Finnish positions in beer, carbonated soft drinks, water, long drinks, ciders and wines and spirits.
Jean-François van Boxmeer, Chair and CEO of Heineken said: "We are pleased to announce this transaction, as we are convinced that Hartwall's future development is best served as part of Royal Unibrew, our long-time business partner in Denmark and an important beverage company in the Nordics and Baltics region.
"We look forward to building on our business in the region working together with Royal Unibrew," he added.
The world's third largest brewer and Royal Unibrew have also agreed to extend an existing partnership whereby the latter has a license to brew Heineken beer for the Finnish, Estonian, Latvian and Lithuanian markets.
Royal Unibrew currently brews Heineken in Denmark and distributes the brand in the Baltic countries.
Hartwall will also remain the exclusive distributor of Heineken's global and international brands in Finland, including Sol, Strongbow, Newcastle Brown Ale, Krušovice and Murphy's Irish Stout.
The company will continue to brew Foster's beer under license in the country.
Henrik Brandt, CEO, Royal Unibrew, said: "We really value Hartwall's market position, strong brands and considerable innovation, and the acquisition of Hartwall supports Royal Unibrew's strategy very well.
"Hartwall and the Finnish market are in many ways similar to our Danish operations, and we are confident that, as a long-term focused owner and in close partnership with the company's management and employees, we will be able to increase Hartwall's commercial and operational strength and thus improve earnings."
Heineken will use the Hartwall sale proceeds - it acquired the firm as part of Scottish & Newcastle takeover in 2008 - to reduce its financial leverage, targeting a Net Debt/EBITDA ratio of below 2.5 times by the end of 2014.
More to follow...