The 33-year-old said in a post on his official Twitter account that the operation also removed a hernia.
Willett over the weekend played at the Memorial Tournament in Ohio, in which he ended up tied for 26th at even par.
On Tuesday the 2016 Masters champion tweeted a picture of himself in a hospital bed.
And it was accompanied by a message that read: “So the pain that kept me awake most of Saturday night turned out to be appendicitis!
“Operation went well, also removed a hernia, add it to having Covid in March, wisdom tooth out in April…all in all, been a great year!”
Meanwhile, organisers of a proposed breakaway golf circuit believe their plans to launch in January 2023 are “entirely feasible”.
But no player will be asked to sign up to the £250million Premier Golf League (PGL) until fears over bans and world ranking points have been addressed.
A rival Saudi-backed Super Golf League (SGL) dominated the build-up to the recent US PGA Championship at Kiawah Island, with 48-year-old Lee Westwood admitting it would be a “no-brainer” to sign a multi-million pound contract at this stage of his career.
In contrast, Rory McIlroy reiterated his opposition and labelled the proposals a “money grab” similar to football’s European Super League which swiftly collapsed following a wide-ranging backlash.
And commissioner Jay Monahan told the PGA Tour’s annual player meeting that players signing up to a new league would face suspension and possible expulsion from the Tour, something which would also impact eligibility for the Ryder Cup.