The 22-year-old played 13 times after arriving at Fir Park temporarily in January and has chosen to extend his time in Scotland further.
Laing was out of contract at the City Ground this summer and was not offered a new contract after failing to make a single appearance for the club.
The former England youth international said: “I’m delighted and after such an enjoyable last six months of last season, I couldn’t be happier.
“I’ve got a bit of security for the next two years at a fantastic club with fantastic fans and a fantastic manager.
“I didn’t have a great start last season, getting sent off in the first game, but after that I hit the ground running and it was a really enjoyable experience. I’m delighted to be back.”
Laing’s signing comes as a further boost to manager Ian Baraclough, who has also secured Marvin Johnson on a new three-year deal.
He joined Motherwell from Kidderminster Harriers in January and scored the opening goal in the 3-0 SPFL Premiership play-off final second leg win against Rangers on May 31.