"Today is the dawn of a new era of a diamond industry in Botswana as we begin this journey with HB Antwerp," President Mokgweetsi Masisi said at the opening of the cutting and polishing facility in Gaborone.
The deal, to be formally signed in coming weeks, "is expected to be a game changer", Masisi said.
"I am extremely happy that the government of Botswana and Antwerp have agreed to a strategic partnership whereby the Government of Botswana will invest in HB Antwerp by acquiring a 24-equity stake in HB Antwerp," he said.
Botswana has become the first country outside of Belgium where the Antwerp-based diamond manufacturer has opened a cutting and polishing operation.
Okavango Diamond Company, the country's state gem trader, will supply rough diamonds to HB Antwerp for five years with all the value addition to take place in Botswana, Africa's leading diamond producer.
This new deal comes as Botswana is negotiating a bigger share of De Beers's diamond sales.
Last month Masisi said the country had been receiving less than it "should get" under the existing 2011 agreement with De Beers.
Masisi warned that his country may sever ties with De Beers if those talks produce a sales deal which proves to be unfavourable to his government.
Forty five percent of the country's GDP comes from the sale of diamonds.
