Rudi Garcia's men have signed the centre-back on a year-long loan deal with the option of a permanent transfer at the end of the season
The centre-back has joined on a year-long loan deal, with Rudi Garcia's men retaining the option to make the transfer permanent at the end of the season.
"The club announces it has sold Davide Astori to AS Roma on a one-year loan with the right to redemption," a statement on Cagliari's official website read.
"Cagliari thanks Astori for the professionalism, devotion and gratitude he has show until his last moment in red and blue."
Astori had only recently agreed a new three-year contract with Cagliari after an impressive Serie A season in 2013-14.
"I have been here six years now and I've grown up and matured while in Sardinia," he said this week.
"I wanted to show my gratitude to Cagliari. I thank president [Tommaso] Giulini: it is a decision we took together."
Garcia had previously confirmed his side were still in the hunt for defensive reinforcements after signing full-back Ashley Cole earlier this summer.
Astori follows Cole and fellow new signings Seydou Keita, Urby Emanuelson and Juan Iturbe to Stadio Olimpico.