The 20-time English champions confirmed on Friday evening that they had reached an agreement with Los Blancos for the signing of the Brazil international.
"Manchester United is delighted to announce that the club has reached agreement with Real Madrid for the transfer of Casemiro," read the statement.
"The transfer is subject to the agreement of personal terms, UK visa requirements and a medical. Casemiro has played over 500 professional games, including 63 at international level for his native Brazil.
"He has won 17 major honours in his illustrious career including five Champions League titles and the Copa America. We all look forward to welcoming Casemiro to Old Trafford."
The 30-year-old is set to undergo his medical with the Red Devils over the weekend, with his debut for the club potentially coming against Southampton in the Premier League on August 27.
Casemiro has taken to social media to pay tribute to Real Madrid and is hopeful that he will be able to return "home" at some stage in the future.
"I have lived the most wonderful story that I ever thought. I hope to return one day to what will always be my home," Casemiro posted on his official account.
"Not in a thousand lifetimes will I be able to give back to Real Madrid and Madridismo all that you have given me. Forever... Hala Madrid."
Man United are believed to be paying £60m for the midfielder, in addition to a potential further £10m in add-ons, with the South American set to pen a four-year deal with the option of a fifth.
Casemiro has been with Real Madrid since 2013, making 336 appearances for the club, contributing 31 goals and 29 assists in the process.
The defensive midfielder made 48 appearances in all competitions last season, as Los Blancos won La Liga, the Champions League and the Spanish Super Cup during a successful campaign.
Casemiro, who is allegedly in line for a huge pay increase at Old Trafford, has won three league titles, one Copa del Rey and five Champions League titles since making the move to Bernabeu from Sao Paulo.
Man United's new signing could be in the stands for Monday's Premier League game against Liverpool, while he should be cleared to train with the Red Devils next week ahead of the Southampton clash. body check tags ::