Massimiliano Allegri's side produced a stirring fightback to beat Roma 4-3 last weekend, but needed no such drama to record a 10th win in its past 13 top-flight games against Udinese on Sunday (AEDT).
Dybala was comfortably Juve's brightest spark and he put it ahead in composed fashion, with McKennie adding a second late on.
The result lifted fifth-placed Juve on to the same points as Atalanta, which occupies the last UEFA Champions League qualification spot, although Gian Piero Gasperini's men do have two games in hand.
Juve was dominant in the early stages and deservedly went ahead in the 19th minute courtesy of Dybala's seventh Serie A goal of the season.
The Argentina international did well to adjust his feet after receiving a deflected pass from strike partner Moise Keane before coolly lifting the ball over the onrushing Daniele Padelli.
Udinese's goalkeeper pushed away a Juan Cuadrado free-kick from an acute angle on the hour mark, while Dybala whipped narrowly wide from the edge of the penalty area.
Yet the result was wrapped up when an unmarked McKennie headed in Mattia De Sciglio's left-wing cross from six yards, the United States international's third league goal of the campaign.