It was the 14th trophy of Guardiola’s remarkable reign at the Catalan giants which began at the start of the 2008/09 season when he succeeded Frank Rijkaard.
To honor their departing coach, Barcelona turned on the style in the Vicente Calderon Stadium in Madrid and the match was effectively over inside the first 25 minutes as Pedro Rodriguez with a double and Lionel Messi scored to put them 3-0 ahead.
The emphatic victory will be consolation in part for shattering defeats to eventual winners Chelsea in the semifinal of the Champions League and the concession of their La Liga title to arch-rivals Real Madrid.
After the Chelsea reverse, the 41-year-old Guardiola announced he would be leaving at the end of the season, bringing to a close a 23-year association with the club as a player and coach.
Guardiola cited tiredness and the need to take a break as reasons for his departure, but he has been linked with a number of vacant managerial vacancies, including Chelsea.
His assistant Tito Vilanova will take charge of Barcelona next season.
They shared the dugout for the final time as Barcelona rounded off their season and afterwards Guardiola said he left with a special sense of accomplishment.
“Fourteen titles in four years is a very high standard so I am very happy to leave the club in a good position, and tonight we played great for the first 35 minutes, we’ve had a good year with four titles so I leave very satisfied,” he told gathered reporters.
“From (Lionel) Messi I have learned to be even more competitive than I ever was, without him we would not have won the number of titles we have and I’m very privileged to have coached who for me is the best player I have ever seen.”
Barca’s 2011/12 campaign had begun in the usual all-conquering fashion for Guardiola and his men as they collected the Spanish Super Cup, beating Real Madrid, the European Super Cup and their second Club World Cup.
But Real took advantage of rare slips by the three-time reigning champions to forge clear in La Liga, the title sealed by a 2-1 win at the Nou Camp last month.
I’m very privileged to have coached who for me is the best player I have ever seen
Pep Guardiola on Lionel Messi
A 2-2 home draw to Chelsea, losing 3-2 on aggregate, prompted Guardiola’s shock departure and left the Copa del Rey as their only remaining target.
Marcelo Bielsa’s Bilbao were expected to offer stiffer resistance but defeat to Atletico Madrid in the Europa League final and disappointing late season form in La Liga was reflected in their performance.
Pedro, who has endured a mediocre season, thumped home the first after three minutes and Messi made it 2-0 with his 73rd goal of the season for Barcelona soon afterwards.
Pedro’s low strike on 25 minutes settled all doubt about the eventual outcome although Fernando Llorente looked to have a strong penalty claim when pulled down by Gerard Pique.
Bilbao had the better chances after the break but Barcelona’s stars coasted to their third victory in Spain’s domestic cup competition in four years to provide a fitting finale for Guardiola.
Editors note: Read Chris Murphy’s feature on CNN World Sport Monday that asks: Did Pep Guardiola reinvent football in his time at Barcelona?