The 400-year-old castle, which has been used as stage set for Sherlock, Doctor Who and Torchwood, will reopen in April featuring a new purpose-built Courtyard Hall conference venue capable of hosting 320 delegates theatre-style or 200 for a banquet.
The Courtyard Hall has been designed to be energy efficient, with heat-retaining and heat-reflective glass, low-energy lighting and a natural grass and wildflower roof. Five further meetings rooms will be made available in the castle itself, each hosting between 10-100 delegates theatre-style.
Phase two of the project will include the introduction of 30 bedrooms and a high-end restaurant with 120 covers, expected to be open by late 2016. Both the castle and its conference facilities will be available for exclusive hire.
Hensol Castle forms part of the Vale Resort, six miles outside of Cardiff city centre and comprising a 143-bedroom, four-star hotel, two championship golf courses and 13 meeting and conference suites, the largest holding up to 700 guests theatre-style.
Stephen Leeke, managing director of the Vale Resort, said: "This is a really exciting investment for the Vale Resort and another significant milestone for us as a business. The conference and event market is an important revenue stream for the Vale Resort, currently representing 25% of our business, and we anticipate significant growth in this sector on the back of this project.
"The historic Hensol Castle gives us another string to our bow by providing an alternative option from our current contemporary offering at the Vale Resort. Event organisers can now choose from two very different venues that offer a combined total of 18 conference and meeting suites."
Hensol Castle reopened to the public last year after being closed for almost a decade.
This year, the Vale Resort will host the National Tourism Awards, UK Coaching Summit 2015, Royal Mint Annual Awards Dinner, South Wales Chamber Welsh Business Awards, and the Wales Head Teachers conference. It has also been chosen as a Rugby World Cup training venue.