TV businessmen Peter Jones and Theo Paphitis have sold the gift experience company Red Letter Days, which they saved from collapse, to rival SmartBox.
Both companies sell balloon flights, spa breaks and other activities for people to give each other as presents.
The two stars of BBC Two's Dragon's Den bought the company out of administration in 2005.
Mr Jones said they were selling the company, for an undisclosed price, because "the time felt right".
Red Letter Days now has more than half a million customers a year.
Last year it made a profit of £1.9m on a turnover of £26m, according to documents filed with Companies House.
The business was not pitched as an idea on the Dragon's Den programme, though both investors are longstanding participants in the show.
Mr Jones is still involved, but Theo Paphitis left in 2012. They each own half of the company.
The SmartBox group, based in Dublin, offers gift experiences in a number of European countries, including the UK where it operates the Buyagift website.