Ward was on hand to convert after his initial 67th-minute shot had been parried by Andy Lonergan and, with Leeds unable to respond, Nigel Clough's men hung on for what was just a second win in nine and a first clean sheet in 15 but a sixth straight win over Leeds.
The full-time whistle marked a second straight defeat for Leeds and they are now three games without a win. Chairman Ken Bates has already turned the heat up on manager Simon Grayson, celebrating three years in charge on Boxing Day, by demanding promotion this season, but this was not the performance of a side destined for better things.
A late flurry apart, United created no genuine chances and, although Derby offered up little more, they did signal some intent when Ward hit the post in the first half and could lay claim to being deserving winners.
Derby did the double over Leeds last season, with their 2-1 victory at Pride Park in April putting the skids on Leeds' ultimately fruitless chase of a play-off place, and the away side started as though they had revenge on their minds.
A slip from John Brayford allowed Aidan White a run which Shaun Barker halted, with Michael Brown drilling wide through a crowd of bodies from the subsequent corner.
After surviving that early flurry, Derby settled and Nathan Tyson, making an injury-delayed first start since his summer move from Nottingham Forest, should have done better than warm Lonergan's palms when he got free in the 15th minute.
Leeds' leading scorer Ross McCormack then fizzed in a 35-yard drive out of nothing that Frank Fielding had to scramble to turn away, before Ward went the closest out of anyone when he worked an opening and crunched an effort into the base of Lonergan's post.
The former Sheffield United winger got the better of Tom Lees and found half a yard inside the box, with the strike rebounding into the path of the onrushing Paul Green who should have done better than bundle it away from goal.
It was then Leeds' turn to go close, with Scotland winger Robert Snodgrass at the heart of their chances. His jinking run was halted by Gareth Roberts and, from the subsequent free-kick from the corner of the box, his stinging hit was tipped over by Fielding. His corner then found Luciano Becchio free but he headed over from six yards out.
A scrappy 10-minute period preceded the half-time whistle but Derby emerged the better side after it, with Roberts slicing wide when a chance presented itself to him on the edge of the area.
Patrick Kisnorbo then flicked a header over for Leeds and Fielding beat away an opportunist drive from Danny Pugh as the game opened up, but the pace of Derby's attack always promised to cause problems and so it proved as they opened the scoring.
Craig Bryson's neat ball played Ward in on the left of the box and, although his first effort was smothered by Lonergan, the ball came free and he duly tucked in his third of the season.
Leeds response was not immediate and it took 20 minutes for them to test Fielding, with the former Leeds loanee keeping out a McCormack drive and then Adam Clayton's follow-up effort. The keeper also did well to push out a Kisnorbo header, but Leeds' charge had come too late.
