Omphile Ramela was the star of the final with the bat, hitting 54 in just 34 balls as the Cobras racked up 158 for four after winning the toss and electing to bat.
Dane Paterson then claimed 4 for 33 and Dale Steyn conceded just 11 runs in his four overs as the Knights were restricted to 125 for nine.
The two innings followed very similar paths up until the last five overs, when they diverged very swiftly.
The Cobras hit just two boundaries in the powerplay, from which they scored 28 for one, and saved their big hitting for the last nine overs, which yielded 104 as Kieron Pollard (43 not out from 23 balls) joined Ramela in a 68-run stand.
The Knights were slightly more adventurous up front and were within a run of the Cobras at the halfway point, but fell apart entirely as the chase moved into its final phase.
While the Cobras took 68 from their last five overs, the Knights lost five wickets for nine runs in two overs as their challenge went up in flames.
Cobras captain Justin Ontong made less obvious but equally important contributions to the Cobras cause.
He used Steyn at important junctures to put pressure on the Knights batsmen, broke the key stand between Reeza Hendricks (41) and Rilee Rossouw (33) when he had the former caught and bowled, and went on to take five catches in the innings.
Michael Owen Smith