Frankie Muniz, who played the titular character for all seven seasons between 2000 and 2006, posted snaps of the happy event on Instagram yesterday (September 18).
He was joined by the likes of Breaking Bad's Bryan Cranston and Jane Kaczmarek, who played his parents Hal and Lois, as well as on-screen siblings Christopher Masterson (Francis), Justin Berfield (Reese) and James and Lukas Rodriguez (Jamie).
Erik Per Sullivan - who played Dewey - was apparently unable to attend, but was represented with a current picture in a group shot of cast and crew.
Another image featuring Muniz and Masterson joking with Cranston was captioned "he is the danger", a reference to the 56-year-old's Breaking Bad character Walter White.
Muniz took to Twitter during the reunion to announce that he was having "an amazing time" with his "old friends", despite apparently suffering from food poisoning.
"[I] realised how much I missed everyone," he added.
Watch the opening to Malcolm in the Middle below: