He posted a 3-under 69, his fourth round in the 60s, to win the event by five shots at 17-under-par 271. The win was Howell's second of the season and his fourth on the European Tour.
Howell earned enough world ranking points that when the Official World Golf Rankings come out on Monday, he is expected to move into the top 10. He became the second multiple winner on the 2006 European Tour schedule and his five-shot win is the largest margin of victory on tour this season.
'It didn't feel easy, trust me,' said Howell. 'I had too big a lead and my play over the front nine gave me that little bit of comfort. This BMW Championship is our flagship event. It doesn't come any bigger than this in Europe. I never dreamed I get my name on this trophy. I'm very honored and humbled to join the fantastic list of winners.'
Simon Khan birdied his final two holes Sunday to shoot a 44-under 68. He finished alone in second place at minus-12, one shot better than Miguel Angel Jimenez, who carded an even-par 72 in the final round.
Brett Rumford fired a 7-under 65 on Sunday to take fourth place at 9-under-par 279. Richard Bland shot a 4-under 68 in round four to finish alone in fifth at minus-8.
Howell began the final round with a three-shot lead, but wasted little time in extending that cushion. He drained a 9-foot birdie putt at the second, then collected back-to-back birdies from the fourth, where he two-putted for birdie. The Englishman ran home a 35-foot birdie putt at five to get to 17 under par.
Jimenez, who played in the final group with Howell, never mounted a charge on the front nine. He mixed two bogeys and a birdie, but when an errant 6-iron from Howell at the 10th led to a bogey, Howell's lead fell to six.
'My plan was to play a solid round of golf from tee to green and try and put Miguel under pressure,' said Howell. 'I was able to do that on the front-nine holes.'
On the second nine, armed with a six-shot lead, Howell played conservatively. At the par-5 12th, Howell reclaimed the lost shot at 10 when he two-putted for birdie from 25 feet.
That would be Howell's last birdie, and through most of the remaining holes, Howell never found trouble. His best look at birdie came at the 14th when he had 12 feet from the back fringe. Howell came up short with that putt, but his drive at the par-5 17th served as a minor hiccup. He hit it in the right rough and received a free drop. Howell pitched into the fairway, then knocked his third to 18 feet. The Englishman missed the birdie try, but still had the par-5 18th.
He pulled a 3-iron out of the bag and laid up well short of the putting surface with his second. Howell pitched his third to 7 feet, but missed the meaningless putt. He tapped in for par, then visited the winner's circle for the first time since the season-opening HSBC Champions Tournament.
'I always seem to come back strong when I've had a rest,' said Howell, who missed close to a month earlier this year because of a back problem. 'I need to be big enough to take time off when I'm not injured. I'm delighted to come back so strong.'
Khan and Jimenez were battling for second throughout most of the round. Khan birdied the 17th to draw even with Jimenez at 11 under par, but Khan tapped in a short birdie putt at the closing hole to move one ahead.
Jimenez drove into a bunker at the 72nd hole and had an awful stance. He elected to just blast out, which left him with 180 yards for his third. The Spaniard played his third to 18 feet on the left fringe, but missed, dropping him to a solo third.
Padraig Harrington (71), Andrew Coltart (69), Trevor Immelman (65), Gary Orr (67) and Anthony Wall (66) tied for sixth place at 7-under-par 281.
Ernie Els (72) and Retief Goosen (70) were part of a group tied for 19th place at minus-4.