Antonio Conte's side moved quickly to secure the signing of Barkley for a cut-price, believed to be in the region of £15m ($20.3m) with add-ons. The Blues thought they had got their man for over double that figure in the summer, but Barkley decided against a move to west London in August and chose to build up his fitness at his boyhood club, who lost out on £20m as a result.
It was thought that Barkley was holding out for a move to Tottenham Hotspur, who had been credited with a long-standing interest in the 24-year-old, but the now-former Everton star was taken aback by Chelsea's persistence to bring him to the capital and is looking forward to a fresh start away from Merseyside.
"I'm overwhelmed, I'm looking forward to it and I'm really excited to get started," Barkley told Chelsea's official website.
"To be given a fresh start at a new club like Chelsea, it's unbelievable for me. I'm looking forward to continuing where I left off at the end of last season and hoping to improve and add more goals to my game."
Chelsea were advised to sign Barkley by former technical director Michael Emenalo, who also played a big part in the Blues' unsuccessful pursuits of former Everton stars Romelu Lukaku and John Stones, who joined Manchester United and Manchester City respectively.
Chelsea did not want another star scouted and examined by Emenalo to fall by the wayside, according to the Telegraph, and club director Marina Granovskaia is delighted to see Barkley eventually sign on the dotted line.
"Ross is a player we have long admired and are certain he will prove to be an important player for Chelsea. He possesses outstanding technical and physical attributes, matched with good experience of the Premier League and a strong desire to succeed at the highest level. We welcome him to the club and look forward to seeing him in action."
Chelsea boss Conte has touched upon his frustration over recruitment on a number of occasions throughout his spell in London, but he lauded Blues officials for taking advantage of a "good opportunity" in the form of Barkley, who has ended his 13-year association in acrimonious circumstances.
"I think that if there is news then the club will inform you," Conte said in his press conference earlier this afternoon before the deal was confirmed, per Football.London. "We are talking about an English player who is a good prospect for Chelsea. I think the club decided for this investment for the contract. It's a good opportunity to buy this player.
"He has a lot of space for improvement. He's strong physically and has good technique. He had a bad injury and surgery. He's not played for seven months. If the player signs for the club, we must have great patience."