The 33-year-old former captain takes over from Glamorgan wicketkeeper Mark Wallace, who retired on 10 February.
Mitchell, replaced by Joe Leach as captain for 2017, becomes the 14th PCA chairman since its creation in 1967.
"For Daryl to go through the process of being elected by over 400 of his peers show the regard he's held in," said PCA chief executive David Leatherdale.
"There were some strong candidates. But Daryl's been around for 13 or 14 years now. The players know him and what he stands for. He's trusted and respected.
"It's ironic that, having been his boss when I was chief executive of Worcestershire, he's now effectively my boss as chairman of the PCA."
Worcestershire opener Mitchell is scheduled to be in office for the next four years - also the length of the new contract he signed at New Road in December.
He won a closely-contested election ahead of four other candidates - Durham's former England fast bowler Graham Onions, Leicestershire opening batsman Paul Horton, Somerset middle-order batsman James Hildreth and Northamptonshire all-rounder Steven Crook.
Subject to approval at the PCA's AGM on 21 February, Mitchell will be the third Worcestershire captain to fulfil the role, following Tim Curtis (1989-96) and Vikram Solanki (2009-13).
"It's well known now that I wanted to continue as captain," Mitchell told BBC Sport. "I'm not going to lie. It was difficult for me in October but as soon as I made the decision to sign the new contract, that drew a line in the sand.
"Standing for election for this is something I'd have done anyway. I like being busy. But, looking back now, with a bit of water under the bridge, maybe not being captain as well will relieve a little bit of pressure and give me more time to focus on my batting next season.
"It's great to have this new role but I've still got be focused. And it might prove a blessing in disguise in that way."
The other 10 cricketers to have held the role of PCA chairman are Roger Prideaux (1967-68), Jack Bannister (1968-70), Mike Edwards (1970-73), Peter Walker (1973-75), David Brown (1975-80), Chris Balderstone (1980-84), Geoff Cook (1984-89), Matthew Fleming (1996-2003), Martyn Ball (2003-07) and Dougie Brown (2007-09).
Worcestershire's Daryl Mitchell has been elected as the new chairman of the Professional Cricketers' Association.