An investor group including private-equity firm BC Partners and the Canada Pension Plan's CPP Investment Board is investing roughly $2 billion in Suddenlink Communications, valuing the seventh-largest U.S. cable operator at $6.6 billion including debt.

The two investors, along with some members of Suddenlink's management, are buying out existing investors GS Capital Partners, Quadrangle Group LLC and Oaktree Capital Management LP, said representatives of Suddenlink and the investors. GS Capital Partners is the private-equity...