Ross Callachan has joined the club on a one-year deal, with an option of a further year.
The 30-year-old makes the switch to Fir Park after his contract expired with Ross County last month.
“I’m delighted to have Ross at the club,” Manager Stuart Kettlewell said.
“He’s been unfortunate over the past year with certain injuries that forced an extended spell on the sidelines, but Ross has recovered well and is ready to kick on this season.
“Ross is an experienced professional especially throughout Scottish football, and we believe he can really add quality to our midfield.”
“I can’t wait to get back onto the pitch,” Callachan said.
“Last year was a tough season for myself personally, but my recovery has gone to plan and the opportunity to play for Motherwell was something I simply couldn’t turn down. This feels like the perfect next step in my career.”
Centre midfielder Callachan represented Raith Rovers at youth level before joining their first-team in 2010, making his senior debut at the end of the 2010/11 season.
After seven appearances the following season, he spent some time out on loan with Mussleburgh Athletic.
He then became a regular feature for Raith Rovers in the seasons that follow and accumulated over 160 appearances before moving to Hearts for an undisclosed fee in 2017.
In his only season in Edinburgh, he made 25 appearances, scoring four goals before switch to St Johnstone.
After 18 months at McDiarmid Park, he made a loan move to Dens Park in the January of 2020. His short stint in Dundee would be tainted with injury as the midfielder suffered a leg fracture and only made four appearances.
Once football returned following the Covid-19 lockdown, he joined Hamilton Accies in the Premiership. He spent one season at Hamilton, where he was a shining star in the side that were eventually relegated. He scored 10 goals from the middle of the park and come the end of the season, interest was high.
Ross County eventually won the race for his signature and he moved to Dingwall in the summer of 2021. In his first season, Callachan became an integral part of the Staggies’ side that went on secure top-six status. His initial two-year deal was extended by a further two years, which kept him at the club until 2024.
He had made 28 appearances the following season, 22/23, before he ruptured his ACL in a match against Celtic in April 2023. That injury kept him sidelined for over a year before he returned to Ross County’s bench in May 2024.
With 126 Premiership appearances, and 127 Championship, Callachan now returns to Lanarkshire with the Steelmen as he looks to pick up where he left off prior to his injury lay off.