Brier, who won this event twice when it was part of the Challenge Tour, pulled away from the field with four birdies on the back nine.
'Unbelievable! I had tears in my eyes on the 18th green,' Brier admitted. 'It's just the best winning at home. Maybe the first one was special because it was my first win on the Challenge Tour, but now on the European Tour where I've been for seven years now, it's really unbelievable.'
Soren Hansen fired a 6-under 65 to take second place at 15-under-par 269. Simon Dyson managed just one birdie, to go with one bogey, in the final round as he ended alone in third at minus-14.
Richard Green set the new course record with his 8-under 63. That helped him jump into fourth place at 13-under-par 271. Gary Murphy took fifth at miuus-10 after a closing 65.
Brier made things interesting early in the final round. He tripped to bogeys on two and three to slip into a share of the lead with Dyson at 13 under.
With Hansen and Colin Montgomerie making charges at the lead, Brier settled in with five straight pars. He then two-putted for birdie on the par-5 ninth.
'I was hitting the ball okay early on,' Brier said. 'I was getting a little bit shaky, but I made a few good swings on five and six and that got me into the game. With the birdie on nine, that got me going.'
However, when he parred the 10th, Hansen joined him in the lead at 14 under. Hansen was on fire to that point with birdies on five, eight, nine and 10. He poured in his fourth straight birdie on No. 11 at Fontana Golf Club to tie Brier at minus-14.
Brier responded to the challenge with a 7-foot birdie putt on the 11th to regain the lead. He drained a long birdie putt at the 13th to pad his lead to two strokes over Hansen.
The Austrian two-putted for birdie at the par-5 15th and closed with a two- putt birdie from the back fringe at the par-5 closing hole for the final three-stroke margin.
'When I got my second shot over the water, I just had to really calm down,' Brier said. 'It was my goal to win and I didn't have a good season until this week. I didn't miss a fairway all day and never got into big trouble so that was key.'
Hansen two-putted for birdie at the 15th, but gave that stroke back with a bogey at the next. He did close with a birdie to end alone in second.
'I didn't really think I had a chance to win with the way Simon and Markus played all week,' stated Hansen. 'I just wanted to have a good go at it. I haven't played well for a long time. It was just a little bit unfortunate on 16 I made a stupid bogey with a wedge in my hand, but otherwise I played fantastic.'
Dyson, who played alongside Brier, tripped to a lone bogey at the third, but still shared the lead at that point. However, he parred the next 12 holes before a birdie at 16 helped him shoot even par for his round.
'I am very disappointed. I struck the ball beautiful again from tee to green,' Dyson admitted. 'I just didn't hole a thing on the greens all day. The 9-foot putt I holed on 16 was the longest putt I made all day. For four days, that's the best I've struck it, ever, probably.'
Montgomerie, the eight-time Order of Merit winner, ran off three straight birdies from the second to move within one of the lead at 12 under. However, he struggled mightily on the back nine with three bogeys and two double bogeys. That dropped him all the way into a share of 13th at minus-5.
Miguel Angel Jimenez (67) and Jean-Francois Lucquin (69) shared sixth place at 9-under-par 275. Emanuele Canonica, Darren Fichardt and Steven Jeppesen were two strokes further back at minus-7.