Wales was matched by Italy in the try count with two each, and recalled flyhalf Stephen Jones made the difference with his boot, kicking over four of five attempts.
By contrast, Mirco Bergamasco missed both conversion chances, and he substitute flyhalf Luciano Orquera squandered 10 points in total off the tee, leaving Italy ruing a third straight defeat in the championship after the one game it targeted as the most winnable.
Center Gonzalo Canale took advantage of a dropped pass by Wales lock Barry Davies to score an early try for Italy, then winger Morgan Stoddart and flanker Sam Warburton crossed to boost Wales to 21-11 up at halftime. Italy captain Sergio Parisse then drove over to cut the deficit to five, but despite dominating the second half his side couldn't show it on the scoreboard.
When Wales finally made it back into Italy territory, Wales jack-of-all-trades James Hook sealed the win with a drop goal six minutes from time.
Wales, wary of Italy after losing in Rome in 2003 and 2007, grabbed the lead in the second minute. Flanker Robert Barbieri was penalized for not releasing lock Alun-Wyn Jones in the tackle and Jones kicked the first points.
Italy hit back immediately. Davies threw a loose pass that went to ground, Canale pounced on the ball, chipped through and dived on the ball over the line. Bergamasco couldn't convert and the host's lead lasted four minutes.
Hook shrugged off Canale's attempted tackle, popped the ball to fullback Lee Byrne and he offloaded to Stoddart, who twisted through Canale and scrumhalf Fabio Semenzato to go over in the corner. Stephen Jones missed the conversion from wide out.
Again Italy responded quickly. Flyhalf Kristopher Burton chipped over the Wales defense, Byrne and Stoddart allowed the ball to bounce and after Bergamasco tackled Stoddart, the wing was penalized for not releasing. Bergamasco picked himself up to kick the penalty and level the scores at 8-8.
Wales continued the tit for tat by immediately racing up the other end for its second try. Shane Williams fielded a Semenzato kick, and released Byrne to break through the midfield. Hook was on his shoulder to continue the move and he drew fullback Luke McLean and offloaded to Warburton for a simple run in between the posts that Jones converted.
Italy's problems continued at the lineout, and Alun-Wyn Jones stole Italy's first two throws. Eventually they were rectified and from one Italy felt it scored its second try.
Flanker Alessandro Zanni took the lineout, and Burton's pass sent center Alberto Sgarbi crashing into Wales' defense. Santiago Dellape drove on and when the ball came back, Burton sent play the other way to Bergamasco and Semenzato on the left wing.
The pair was stopped short of the line, but from the ruck Zanni dived over the pile. While the TV official ruled out the try for Stoddart holding up Zanni, referee Wayne Barnes instead awarded Italy a penalty that Bergamasco kicked to make it 15-11.
Wales kept up its attack and Bergamsco stopped inside center Jamie Roberts close to the line, and Italy winger Andrea Masi put in a try-saving tackle on Ryan Jones to stop an overlap when the No. 8 had three players free outside him.
Wales finished the half with Stephen Jones kicking two more penalties for a 10-point lead at the break.
After a frenetic opening to the second half, Wales captain Matthew Rees put in a neck-high tackle on Burton but Bergamasco pushed the resulting penalty wide.
Eventually, Sgarbi and Canale chased a kick and stole the ball from Williams as the winger chased back. Semenzato went left from the ruck and Parisse powered through Stephen Jones and Mike Phillips for Italy's second try.
Midway through the half, Bergamasco was overlooked for a penalty attempt and Italy went for touch. Another penalty was turned into a five-meter scrum but Italy's chance was ruined by good scrummaging from Wales.
With the next penalty chance, Orquera kicked wide and when Masi kicked straight to touch, Wales broke into Italy's 22 and Hook celebrated his 50th cap by slotting a drop goal to secure the win.
With the clock ticking down, Orquera put Canale through but Bergamasco knocked on with the line at his mercy.
— Wales 24 (Morgan Stoddart, Sam Warburton tries; Stephen Jones 3 penalties, conversion, James Hook drop goal), Italy 16 (Gonzalo Canale, Sergio Parisse tries; Mirco Bergamasco 2 penalties). HT: 21-11.
