After 10 years at City, Aguero passed a medical on Monday to seal his free transfer to Camp Nou, with the Argentina international to officially become a Barca player on July 1.
The striker became City's record scorer during his decade-long stint at the Etihad Stadium, but now he is set to be united with compatriot Lionel Messi in Spain.
"We all know that Barca are the best club in the world, so I think I made a great decision to be here and I hope to help the team," Aguero said.
"Of course it's a step forward in my career. I'm really happy and hopefully I can help the team to win things."
"First of all, I want to play and help the squad and if the team does it well I will be happy individually. I just try to help the team and try to arrive at the end of the season with chances to win titles."
Hit by injuries and COVID-19 in a disrupted final season at City, Aguero bowed out with a substitute appearance in the Champions League final as Pep Guardiola's side lost 1-0 to Chelsea in Porto on Saturday.
Speaking in an interview released on Barcelona's Twitter account, Aguero indicated he had moved on and was now looking firmly to the future.
He said: "I want to send a big hug to everyone, to all supporters. I will try to give my best and hopefully the fans will enjoy my football skills.
"I've changed a little bit - at least my look when I arrived to Europe to Atletico Madrid at 18 years old. I learnt a lot, then I played for City in the Premier League.
"Now I've changed of course my way of playing, but I have an idea where I can play and I will try to help my team-mates with my experience."