Pedro has become the first player to move between fierce rivals Roma and Lazio for 36 years, as the latter announced the Spanish winger's signing on Thursday.
The 34-year-old former Barcelona and Chelsea player has joined Lazio on a free transfer after new Roma coach Jose Mourinho deemed him surplus to requirements.
Pedro, capped 65 times by Spain, is the first player to make the controversial switch since goalkeeper Astutillo Malgioglio signed for Lazio in 1985.
"Introducing our new number nine," Lazio said in a post on Twitter with a photo of Pedro holding a club scarf.
He scored six goals in 40 appearances for Roma last season after leaving Chelsea in 2020 following a five-year spell in London.
Pedro signed for Chelsea while Mourinho was manager and also played under new Lazio boss Maurizio Sarri at Stamford Bridge in the 2018-19 campaign.
According to Italian media reports, Pedro left Roma despite having two years left on his contract.
Lazio kick off their season at Empoli on Saturday.