A tender is out for construction of 40 apartments. An additional 50 chalets are also planned for later stages, along with an extension to the existing hotel.
Celtic Manor is set in a 26,000-acre site in the Usk Valley near Newport. It is owned by Wesley Clover, the investment fund of Sir Terry Matthews.
Wesley Clover chief executive Simon Gibson told the Western Mail that the works would create 700 jobs in the construction supply chain.
In August the resort plans to unveil the longest zip wire attraction in Europe. The Sky Wire Wales will carry riders a mile from the top of the resort across the River Usk to Caerleon at speeds of up to 80mph.