She reportedly died on Monday as a result of complications from cardiac arrest.
Her former co-stars were among those to pay their respects, with Charlie Sheen describing her as an "absolute sweetheart".
Ferrell played cantankerous housekeeper Berta on the popular sitcom, starring alongside Jon Cryer, Angus T Jones, Sheen, and later Ashton Kutcher.
Sheen, who was fired from Two And A Half Men in 2011, tweeted a picture of him and Ferrell on set and described her as "an absolute sweetheart a consummate pro a genuine friend a shocking and painful loss".
He added: "Berta, your housekeeping was a tad suspect, your 'people' keeping was perfect."
an absolute sweetheart
a consummate pro
a genuine friend
a shocking and painful loss.
was a tad suspect,
your "people"keeping was perfect.
— Charlie Sheen (@charliesheen)
Cryer, who played Sheen's bumbling on-screen brother, recalled meeting Ferrell on-set for the first time and said he was already a fan of her work.
He tweeted: "She was a beautiful human Berta's gruff exterior was an invention of the writers. Chatty's warmth and vulnerability were her real strengths. I'm crying for the woman I'll miss, and the joy she brought so many."
Two And A Half Men co-creator Chuck Lorre said: "We called her Chatty. And we all loved her. Twelve years of highs and lows, and lots and lots of laughter. Through it all she was a rock. One of the greats. I was privileged to call her a friend."
Lee Aronsohn, who created the show alongside Lorre, described Ferrell as a "warm, wonderful woman who was always a joy to be around on set".
He added: "My heart goes out to her husband Arnie, who was *always* by her side."
For her role as Berta, Ferrell earned two Emmy nominations. Her film roles include 1976 satirical comedy Network, Tim Burton's Edward Scissorhands and Erin Brockovich, the 2000 biopic starring Julia Roberts.