'It's nice to get going and win again,' said Gronberg.
Jose Manuel Lara and Colin Montgomerie also shot 7-under 65 during the final round to finish in a tie for second place with overnight leader Ricardo Gonzalez. That trio finished at 15-under-par 273.
Gronberg began his move to the top with three straight birdies from the third. He followed that with another birdie at the par-4 seventh.
Around the turn, Gronberg really got going when he eagled the par-5 11th for the second straight day. This gave him the lead at minus-16. Lara, playing ahead of Gronberg, eagled the 16th to join Gronberg in the lead.
'I knew it was getting interesting after my eagle,' said Gronberg. 'I knew I had to play quite good golf and keep it going from there.'
Both men faltered however to briefly create a three-way tie. Gronberg bogeyed the 15th, while Lara dropped a shot at the last. This created a three-way tie with Montgomerie at 15-under.
'That bogey on 14 made it a little bit too interesting, but I came back and made a very, very good putt on 15,' Gronberg said.
The tie did not last long however. Gronberg came right back to birdie the 16th. He rolled in a putt from off the fringe from about 15 feet out to regain the lead.
The Swede followed that with another birdie at the next. He then parred the final two holes to maintain his two-shot lead.
'I got a great putting tip from a fellow Swede after the second round and it really helped,' said Gronberg, who needed just 26 putts in the final round. 'I didn't play so good tee-to-green, but I manage to be great chipping and putting to keep the round going.'
Gonzalez, playing in the final group, was the only one with a chance to catch Gronberg. He needed to play the final four holes in minus-3 however to do so.
The Argentinean, who led by one stroke entering the round, posted a bogey, double bogey, eagle and two birdies on the front nine. Gonzalez also birdied the 13th and 14th to setup his chance over the final three holes.
Gonzalez did his best starting with a birdie at the 16th. However, after coming up short on a birdie chance on 17, he needed to hole his second shot at the last. His tee ball on No. 18 found a fairway bunker. He hit a poor shot short of the green, thus clinching the victory for Gronberg. Gonzalez did get up-and-down for par and a share of second place.
Lara, who began the final round five shots off the pace, dropped a shot at the first. He responded with back-to-back birdies from the second. He continued his climb up the leaderboard with two consecutive birdies from the sixth and again from the 11th.
The Spaniard got into the mix towards the end of the back nine. He birdied the 15th, then eagled the 16th to grab a share of the lead. However, he bogeyed the last to end any chance he had at picking up his first victory on the European Tour.
Montgomerie was hot early and late in his round, but couldn't maintain his torrid pace throughout. He birdied the second and eagled the third. However, he could only manage pars on his next seven holes.
Around the turn, the Scotsman birdied the 11th. He climbed into second place with three straight birdies starting at the 15th.
Simon Khan and Martin Maritz shared fifth place at 14-under-par 274. Pierre Fulke and Fredrik Widmark were one shot further back at minus-13.
Ian Poulter, the 2002 Italian Open champion, shot four-under 68 on Sunday to climb to 9-under-par 279 and a share of 18th place with four other players.