The teams were well balanced in the first half, Cardiff taking a two-point lead at half time courtesy of three Leigh Halfpenny penalties.
Sale made a bright start to the second half, Aston Croall scoring a try in the opening minute to put the visitors ahead. However, the hosts hit back quickly through Lloyd Williams to restore their lead.
A tactical 20 minutes saw few opportunities for either side to score, with little between the teams.
A late surge from Blues saw Michael Paterson cross the whitewash and seal the win for the home team.
The victory is Cardiff's first of the tournament this season, in the last game of the pool stage of the competition.