The striker returns to the Argentine side at which he started his career before going on to enjoy spells at the likes of Manchester United, Manchester City and Juventus
And the 31-year-old, who rejected a move to Atletico Madrid in order to return to the Buenos Aires side, said he has been waiting for a year to return "home" and insisted that he is still in the best form of his career.
"When I left Boca I was 20 years old," he said. "Now, at 31, I'm bigger, more experienced, and I need to be an example for the youngest players. I'm back in my best form at the moment.
"I have been thinking about coming back here for a year.
"I am really grateful to Atletico coach Diego Simeone for his interest, but I chose Boca, my home.
"I want to train tomorrow with my team-mates, and show them on Saturday against Quilmes that I'm in good condition to play.
"Rodolfo Arruabarrena, the coach, knows where I can play and what I can do so I will listen to him.
"Juan Roman Riquelme is my friend. He is the biggest - the idol of Boca. I'm here to write my story, not to replace him."
Mi corazón explota de felicidad!!! Gracias por bancar el frío y por esperarme. Ya estoy en casa