James Hook crossed for a second-half brace of tries to ease Wales to only their second win of the championship and lift the pressure on head coach Warren Gatland.
Wing Shane Williams added a third try while fly-half Stephen Jones scored 18 points, including four penalties and three conversions in a 100 per cent kicking and man-of-the-match performance.
Italy fought to the death and were rewarded for their efforts when full-back Luke McLean touched down for a consolation score.
Wales coach Warren Gatland said that the victory had given them a confidence-boost ahead of a tough southern hemisphere tour of South Africa and his native New Zealand but said that all in all a fourth placed finish did not justify their real standing.
"It's been pretty frustrating and I felt we haven't played to our potential," said Gatland, who came into the match with a certain amount of pressure building on him.
"I am not atall disappointed with this defeat," said the England-born naturalised South African.
"I am very pleased, because it was our most complete performance," said the 32-year-old.
And the 18-year-old showed no fear on his debut as the teenage wing was in the thick of the action from the kick-off.
Gatland had praised Prydie's physical attributes in training and he proved his ability with his first tackle on McLean after just 38 seconds.
Then the Ospreys young gun inflicted his first Test casualty with the help of Gethin Jenkins in s crunching hit to force Italian centre Gonzalo Canale off with a rib injury.
After a frantic opening, with Adam Jones also departed with a head wound Stephen Jones booted the home side into a ninth minute lead.
Bradley Davies became the third player to exit proceedings inside 15 minutes with concussion but the passion and commitment Gatland had asked for prior to the clash was met with an emphatic response when fit-again Jenkins and skipper Ryan Jones doubled up to stop McLean in his tracks.
Jones added a second penalty and after a period of sustained pressure, Wales appeared to have broken the try deadlock in the 28th minute.
But Lee Byrne saw his try disallowed by the officials following a forward pass from Shane Williams.
Wales nudged into a nine-point lead when Jones fired home a long-range penalty in the 32nd minute.
Jones handed Wales a 12-0 interval advantage with his fourth successful kick.
Italy had defended well in the opening period following a horror show in Paris six days earlier but Wales persistence finally paid off.
Byrne was foiled short of the line and after British Lions half-backs Stephen Jones and Mike Phillips combined, Hook fended off the tackle of replacement Tito Tebaldi to score a converted try in the left corner.
Italy then pressed the self-destruct button when Mauro Bergamasco was yellow carded in the 56th minute for coming in from the side.
Gatland's men took advantage imstantly and Phillips and Jones fed Hook for a fine double under the posts.
Jones converted for a 26-0 lead before Mirco Bergamasco finally got Italy on the scoreboard with a penalty on 66 minutes.
Williams looked to have wrapped up the victory with a close-range score after neat build-up from Byrne, Tom Shanklin and Phillips before McLean added a late consolation for the visitors.
Final Score Wales 33 (12) Italy 10 (0)
Scorers
Wales
Tries - Hook 2, S Williams
Pen - S Jones 4
Con - S Jones 3
Drop -
Italy
Tries - McLean
Pen - Mi Bergamasco
Con - Mi Bergamasco
Drop -
Referee: Wayne Barnes (ENG)
Teams
Wales
Lee Byrne; Tom Prydie, James Hook, Jamie Roberts, Shane Williams; Stephen Jones, Mike Phillips; Ryan Jones (capt), Sam Warburton, Jonathan Thomas; Luke Charteris, Bradley Davies; Adam Jones, Matthew Rees, Gethin Jenkins
Replacements: Huw Bennett, Paul James, Ian Gough, Gareth Delve, Dwayne Peel, Andrew Bishop, Tom Shanklin
Italy
Luke McLean; Kaine Robertson, Gonzalo Canale, Gonzalo Garcia, Mirco Bergamasco; Craig Gower, Pablo Canavosio; Alessandro Zanni, Marco Bergamasco, Josh Sole; Marco Bortolami, Quintin Geldenhuys; Martin Castrogiovanni, Leonardo Ghiraldini (capt), Salvatore Perugini
Replacements: Fabio Ongaro, Matias Aguero, Valerio Bernabo, Manoa Vosawai, Tito Tebaldi, Riccardo Bocchino, Matteo Pratichetti
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