The Bayern boss says it is difficult to hear about his former assistant's cancer relapse, expressing his sympathy for the ex-Barcelona coach
The pair have endured a fractious relationship in the media since the revelation Guardiola had not visited Vilanova while both were in New York.
But Guardiola was keen to show his support for his former assistant coach at Camp Nou, who led Barcelona to the Liga title after succeeding Guardiola in the dugout last season.
"He's a friend, and I love him so much," the 42-year-old told reporters.
"It's hard to talk to a friend like Tito in German. I wish the best for him and his family so as to tackle this stage with strength.
"This is very, very hard for me."
Vilanova had been diagnosed with a relapse of parotid gland surgery midway through 2012-13, but appeared to enjoy a turnaround after he made it back to coach Barcelona in the final stages of their campaign.
However, the Catalan club admitted on Friday the trainer would be unable to reprise his duties for the coming season.
The Blaugrana are expected to announce a replacement next week.