The 16-year-old, nicknamed The Killer by his team-mates, was regarded as one of the best youngsters in the youth set-up at Camp Nou and only arrived as a 13-year-old from Malaga.
However, he has shunned their offer of professional terms in order to pen a three-year deal at Anfield.
Pacheco's signing is the latest in a string of youth deals tied up by the Merseyside giants in recent weeks - with Alex Kacaniklic, Marvin Purie, Mikel San Jose, Nikolai Mihailov, Krisztian Nemeth and Andras Simon all penning deals to join the club's academy ranks.
Barca youth coach Garcia Pimienta admitted losing Pacheco was a huge blow to the club.
"It is a great loss for the club because he is a forward with a lot of quality," Garcia told Sport.
"He has been our top goalscorer and has already played for the youth team.
"Alongside Thiago Alcantara and Gai Assulin, he is one of the cadets we had the most hope for, but nothing can be done anymore.
"Everything happened very suddenly."
The news of Pacheco's departure to England is another blow to Barca, who have lost a host of top youngsters to the Premier League in recent seasons.
The likes of Cesc Fabregas, Fran Merida and Gerard Pique have all turned their back on the Blaugrana to make the move to the English top-flight.
I dont think I've see this kid, but I did watch a youtube clip of some young striker doing the business for Barca but I dont know if its this lad. (Probably not
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