Baraclough cut 16 players – including former Hoops striker Scott McDonald – from the Steelmen’s playing staff after surviving a play-off battle with Rangers to maintain their Premiership status.
Now he has snapped up Scotland Under-21 cap Chalmers on a two-year contract as he sets about transforming his group.
The 21-year-old left-back made his Celtic debut against Inverness Caledonian Thistle in August 2012 aged just 18, and has made two other appearances for the Scottish champions.
He spent the second half of the 2013/14 season on loan at Falkirk but now wants to make the breakthrough with ‘Well after another frustrating season back in the Hoops’ youth ranks.
Chalmers said: “I’m delighted to sign for Motherwell and cannot wait to get started. I’ve been in a few times and trained with the lads and it’s a really good group.
“The manager has also been excellent with me and was a huge reason why I wanted to come and play here.”
Well boss Baraclough added: “He’s a young player with fantastic potential who we’ve tracked for some time.
“He’s versatile and will add competition in numerous positions in defence.
“He’s got a good pedigree having come through the academy and played for Celtic’s first team and had significant youth international experience.
“I am really looking forward to working with him over the next few years.”