The Netherlands-based co-operative bought about 3.66 million shares at $3.85 each yesterday.
The shares last traded at $3.87, having sold in Synlait’s initial public offering last year at $2.20 apiece.
The purchase made the Dutch company the second-biggest shareholder in the Canterbury-based dairy processor.
China’s Bright Dairy Food owns 39% of Synlait Milk.
“Our working relationship with FrieslandCampina continues to develop,” Synlait Milk chairman Graeme Milne said.
“They have become both a valued customer and key strategic partner, alongside our other first-tier multinational customers, and we view this announcement as a positive endorsement of the growth and performance of Synlait Milk."
In January, Synlait lifted its forecast milk price for the 2014 season to a range of $8.30 to $8.40/kilogram of milk solids from $8.
It also said net profit would be between $30m and $35m in the year ending July 31, up from the $19.67m forecast in the company’s prospectus.
Milne said at the time that the company was benefiting from growth from its value-add products and a favourable product mix.
Dairy products have helped drive New Zealand’s terms of trade to a 40-year high and made China the nation’s biggest export market.