Twenty hectares of the 143ha estate in Appledore, Kent, was planted with Chardonnay, Pinot Noir and Pinot Meunier in 2003 and Gusbourne has gone on to win international awards.
The money will go to expanding the planted area and increasing the capacity of the winery.
Barclays said further investment and expansion is planned over the coming years.
Gusbourne chief executive Ben Walgate said: “We see further market growth opportunity for the company’s premium English still and sparkling wine products both domestically and internationally.
“The expansion of the business at Gusbourne Estate in Kent will involve further vineyard plantings as well as an enlarged winery and visitor centre to attract the growing interest in wine tourism. We are very proud to be part of the Kent community and will remain closely involved with it as the business expands.”