The 38-year-old announced his decision on social media on Wednesday night but could not be reached for comment yesterday.
The Volts still have three one-dayers remaining in the round robin, so Broom will be able to add to what has been a remarkable career.
The right-hander had a couple of cracks at retiring from red ball cricket before it stuck at the end of the 2019-20 season.
And, in February last year, Broom cited ageing role models Brad Thorn and Ryan Giggs to help ward off questions about life after cricket.
"What a ride ... after 20 seasons playing this great game I’ve decided to hang ’em up at the end of the season," he wrote on Instagram.
"Thanks to all my teammates, coaches, and anyone that I’ve crossed paths with!
"To Otago Cricket thanks for taking me in all those years ago ... I love playing for the blue n gold!
"Mum, Dad, Pete [and] Darren always appreciated the support. Finally, and most importantly, my amazing wife Mel. Thank you for all you’ve done for me and our 5 beautiful kids!!"
Broom began his career in an all-star Canterbury side in 2002-03. But with regular opportunities eluding him, he shifted south to Otago in 2005-06.
He quickly established himself in the starting XI and was called into the Black Caps one-day and T20 sides in 2009.
He went on to play 39 ODIs, 11 T20s and, late in his career, a couple of tests.
But it was at domestic level where Broom shone. He forged an impressive career for Otago that would take him to the top in two of the three most important lists for a batter.
He has scored more one-day runs (4157 at 41.15) and more T20 runs (2926 at 27.09) for the province than anyone else.
And only Craig Cumming (6589 runs) has scored more first-class runs for Otago than Broom, who notched 6085 runs at an average of 40.56, including 15 hundreds and 23 half-centuries in 101 games.
Warren Lees (108) is the only player to amass more first-class games for Otago.
Broom features in two all time first-class partnership records for Otago. He combined with Shaun Haig to put on 306 for the third wicket against Central Districts at Nelson Park in 2009-10, and added 239 for the fourth wicket with Nick Beard against Auckland in Dunedin in 2012-13.
Meanwhile, Otago will host Auckland in a Plunket Shield game at the University Oval today.
The Aces have named uncapped duo Matt Gibson and Simon Keene. Legspinner Adithya Ashok is also in line to make his first-class debut, having carried the drinks during the Aces’ four-wicket win at home last week.
Otago has named debutants Jacob Cumming and Thorn Parkes in its line-up.
