The Chile international will undergo a medical on Monday before putting pen to paper on a five-year contract.
Sanchez, 22, has been heavily linked with the European Cup winners for the majority of the summer, but there was also interest from the likes of Chelsea and Manchester rivals United and City.
On the move: Barca new boy Alexis Sanchez (left) in action for Chile
Barca coach Pep Guardiola has made no secret of his admiration of the pacey winger and has now finally got his man after negotiations between the two clubs.?
A Barcelona statement said: 'Udinese and FC Barcelona have reached a definitive agreement for the transfer of Alexis Sanchez.
'The medical, signing of his contract for the next five years and presentation will take place on Monday.'
Sanchez spent three seasons in Udinese, and scored 12 goals in 31 appearances in Serie A last term to help the club finish fourth and qualify for the Champions League.
He was also a member of the Chile squad which reached the quarter-finals of this summer's Copa America, where they were beaten by Venezuela.
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Source: Daily Mail
Source: Daily Mail