Advent International is expected to close the deal for Craegmoor today, July 18, four months after the care home operator was put on the market.
TDR, another buyout firm and one of Advent's main rivals in the auction, withdrew its interest in June after it was asked to raise its offer.
It was reported that TDR had a number of concerns over the business, such as the availability of finance.
Craegmoor was put up for sale by its owner LGV Capital, the private equity arm of Legal & General.
LGV acquired the group from private equity firm Warburg Pincus in 2001 for £220 million.
Care home sector
Reports suggest that Advent will use Craegmoor as a platform for consolidation in the residential care home sector.
Craegmoor operates 250 care homes and day care centres and provides care to the elderly and to people with mental health problems.
It has annual revenue of about £170 million.
Last year losses at Craegmoor widened from £19.8 million to £24.3 million.