Deutsche Post, Germany's former postal monopoly, has agreed to sell to Deutsche Bank a 29.75 percent stake in Postbank at €57.25 per share in cash, a joint statement said.
It also agreed to grant Deutsche Bank an option to buy a remaining 18.0 percent in Postbank for €55 per share, the statement said following a meeting of Deutsche Post's supervisory board at the firm's Bonn headquarters.
Once Deutsche Bank's stake goes over 30 percent, it will be obliged to make an offer for all remaining shares listed on Germany's blue chip DAX 30 index. Deutsche Post also has the option to force Deutsche Bank to buy its remaining 20.25 percent - but for only €42.80 per share. Both options can only take place within a certain time period after the first tranche is sold.
In accepting the offer, Deutsche Post has rejected a rival but reportedly lower bid from Spanish bank Santander for all of Deutsche Post's Postbank stake. Deutsche's offer was also helped by political support for an all-German deal.
It will fund the deal by raising up to €2.0 billion via a capital increase - issuing and selling more shares in itself - the timing of which will depend on market conditions. Postbank has Germany's biggest retail banking network with more than 14 million customers, and through the acquisition Deutsche Bank will effectively more than double its own domestic client base of just under 10 million.
"Deutsche Bank's and Postbank's service offering, which together include by far the biggest branch network in Germany, is highly complementary with attractive opportunities for cross-selling of financial products," the statement said.
The two have agreed to cooperate in several areas including the distribution of home finance and investment products, producing "substantial revenue potential for both partners," they said.
The announcement came less than two weeks after the announcement of another major deal that promises to shake up high street banking in Europe's biggest economy: Commerzbank's €9.8-billion purchase of Dresdner Bank.
This merger of Germany's second and third largest banks meant that 138-year-old Deutsche Bank was being leapfrogged in terms of branches and customers, although it remains the country's biggest lender in terms of assets.
In July the retail banking sector, where cooperatives and state-owned Sparkassen savings banks have a strong presence, saw another major deal when France's Credit Mutuel bought Citibank's German business for €4.9 billion.
Unlike Commerzbank's deal with Dresdner, which is set to result in the loss of 9,000 jobs, Deutsche's tie-up with Postbank "will have no impact on branches, jobs or the brand of Postbank," the statement said.