Trentino only received a wildcard after finishing third in the European Champions League in March but won five matches in a row in the seven-day event.
Captain Matey Kaziyski led the charge in the final, upsetting the opposition's rhythm with a series of point-scoring spikes in a 25-18 25-15 29-27 victory at the Aspire Zone Hall.
Sada Cruzeiro, who won the South American club championship in September after losing only one set, looked tired after their exhausting 3-2 semi-final win over Zenit Kazan and did little to trouble Trentino.
"It was a very strong championship and it's great to win the title for the fourth time," Kaziyski said.
Led by Serbian Aleksandar Atanasijevic, who top-scored with 22 points, Poland's Skra Belhatow grabbed third place after staging a dramatic comeback to defeat European champions Zenit by three sets to two.
The victory was sweet revenge for Skra who were beaten by the Russians by the same margin in the Champions League final.
The Polish team finished second in the world club championship in 2009 and 2010.