Following confirmation on Sunday night that Barca and Arsenal had reached an initial agreement for the transfer of the Spain international, Fabregas this morning undertook a two-stage medical before the Catalan club confirmed on their official Twitter page that he had put pen to paper on his contract.
The 24-year-old, who has had a 200 million euro (over £175million) buy-out clause inserted in his contract, is now set to be officially presented to the Barca fans on Monday at the Nou Camp before then speaking to the media.
Barcelona posted a comment on their official Twitter feed which read: "Cesc has signed his contract which ties him to Barcelona until 2016. The buy-out clause is 200 million euros."
According to the Barcelona website, Fabregas' medicals have proven him to be in perfect condition.
Barcelona's first-team doctor Ricard Pruna said: "All the tests taken have been satisfactory."
Pruna added that Fabregas "can be integrated into training without any problem".
Barca's next match sees them take on Real Madrid in the second leg of the Spanish Supercopa at the Nou Camp on Wednesday night. Barca drew 2-2 in the first leg at the Bernabeu on Sunday night.
The announcement brings to an end the long-running transfer saga and sees Fabregas return to his local club Barca, who he left for Arsenal as a 16-year-old.
While the Gunners were always determined to keep Fabregas, it became clear this summer that the Spaniard - who made more than 300 appearances for the London club, scoring 57 goals - was no longer committed to their cause.
Barcelona saw a £27million offer rebuffed earlier in the summer, as Arsenal remained steadfast in their demands over a £40million fee.
However, with Barcelona not willing to significantly increase their cash bid, and Arsenal manager Arsene Wenger admitting the player was unsettled, the English club reluctantly have allowed a deal to go through.
Wenger expressed disappointment at Fabregas' departure.
"We have been clear that we didn't want Cesc to leave and that remains the case," he said in a statement on Arsenal's website.
"However, we understand Cesc's desire to move to his hometown club and have now accepted an offer from Barcelona.
"We thank Cesc for his contribution at Arsenal and wish him future success."
Fabregas had, according to Arsenal, been struggling for match fitness because of a hamstring injury which saw him miss the club's Far East tour and other pre-season games.
Wenger omitted his captain from the Emirates Cup pre-season tournament and the midfielder was not selected for Saturday's opening Premier League fixture at Newcastle.
Despite winning both the European Championship and World Cup with Spain, club success has not followed for the midfielder, who missed Arsenal's Carling Cup final defeat to Birmingham at Wembley earlier this year through injury.