The 21-year-old, who is the brother of Bayern Munich midfielder Thiago, thrived for Celta during his season-long loan in Vigo.
However, the attacker has now returned to his parent club and will battle for a first-team spot at the Camp Nou next season.
"Now, a new stage begins. New challenges I will face very happy, motivates and proud to say that I spent an unforgettable season at your side. I love you Celta, I'll see you soon, Hala Celta!" he said in a statement.
"It was a very unique feeling: with your support, it felt like I'd been a Celta player for years and it was only one season. But what a season! I'll never forget the 15th July when, for the first time, I was presented in Balaidos, I felt an indescribable love. And again on the 19th August, my debut defending this great crest.
"I tried to give my best to help the club reach their objectives. And, proudly, we can say that we did."
Rafinha has been with Barcelona since 2006.