With the game moving into stoppage time, home full-back Craig Woodman fouled substitute Ben Muirhead after losing control of the ball in the box and Kennedy stepped up to rattle the resulting penalty past keeper Frank Fielding.
It was no more than Rochdale's efforts had merited after missing a host of chances in a closely-fought game.
In a first half dominated by both defences and lacking in real quality, Dale had the better of the openings that were on offer. In the 30th minute Adam Le Fondre shot over after a neat interchange with David Perkins and then Kennedy fired a 25-yard free-kick just wide of Fielding's post.
The Wycombe stopper was again called into action on the stroke of half-time, saving excellently with his feet after new Rochdale loan signing, Rene Howe, was put clear by Gary Jones. Matt Bloomfield had Wycombe's only chance, shooting straight at Sam Russell from the edge of the box.
The second half though, saw the game burst into life. First Dale skipper Gary Jones fired wide after being put clear by Rory McArdle and then Howe wasted a golden chance, shooting over from eight yards after latching onto John Doolan's cross.
Le Fondre was also unlucky not to score, Fielding saving well at the second attempt after the striker had got in behind the Wycombe defence.
The home side's best moments came when Rochdale keeper Sam Russell made a smart save to keep out David McCracken's header from Russell Martin's cross and substitute Stefan Oakes curled a 25-yard free-kick just wide.
Despite a late onslaught from the hosts, the visitors held on to claim all three points.