Defender Alba has put pen to paper on a deal until June 2020 while Pedro has extended his stay until 2019.
Barcelona have confirmed both deals have release clauses of 150m euros.
The pair agreed the contracts last week but have signed them a day after Barca announced the capture of Aleix Vidal from Sevilla.
Alba joined Barcelona from Valencia for 14m euros in 2012 while Pedro joined the youth set-up at the age of 17.
Pedro had been linked with a move away from the Champions League winners in search of more regular first-team football.
However, he will now continue at the club where he has won five La Liga titles and the Champions League three times.