An eventful contest was settled by strikes from the Italian strike duo to earn the Friuli another crack at Europe's premier cup competition next season.
Guidolin's men were quick out of the blocks and took the lead through talisman Antonio Di Natale's lovely 18th minute strike. Catania was awarded a lifeline before the break, but saw Argentine forward Alejandro Gomez screw his penalty wide. Udinese made sure of the three points on the hour with Diego Fabbrini slotting home after a slaloming run.
The Friuli, who lost to Arsenal in the Champions League qualifiers earlier this season, will now have their eyes firmly on reaching the group stages next time round.
Di Natale atoned for an earlier miss, racing onto Maurizio Domizzi's through-ball to score his 23rd of the season with a fantastic dinked finish from an acute angle.
The Elefanti were certainly not out of the contest, but - though lively in attack - they were creating little.
However, the home side's persistence paid off on 38 minutes when Friuli midfielder Roberto Peyreyra ill-advisedly dangled out a leg, which Andrea Catellani promptly fell over after minimal contact. Gomez stepped up to take the spot kick, but directed a poor effort wide of Handonovic's post.
Udinese reasserted itself after the break and calmed the nerves on the hour. Fabbrini finished off a fine solo run with a firm low finish.
Victory was assured, but Kwadwo Asamoah nearly put further icing on the cake when he hit the post for the visitors.
Guidolin's side saw the game out and his delighted troops will now recharge their batteries this summer as they look forward to a Champions League qualifier next term. Vincenzo Montella's Catania, meanwhile, will look to build on a creditable mid-table finish this season.
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