The two stars reconnected with Jane Kaczmarek, Justin Berfield and Christopher Masterson in Los Angeles on Sunday (16Sep12) and Muniz, who played the title character, shared photos of the get together with fans on Twitter.com.
In a post on Sunday, he wrote, "Had an amazing time seeing all my old friends from 'Malcolm' today... Realized how much i missed everyone!"
But it wasn't all great for Muniz as he was battling a stomach bug too.
He added, "I would get food poisoned the day of the first 'Malcolm In The Middle' reunion. My luck!"
Malcolm in the Middle aired for seven seasons between 2000 and 2006.