Leicester-born Cockerill-Mollett is a product of the club's Academy having made his way through the ranks to sign professional terms in August 2016, before going on to make his first-team debut during a 5–2 EFL Trophy victory over Grimsby Town later that month.
A stand-out performer for the club's Under-18s side, Callum also enjoyed loan spells with Chasetown and AFC Telford United before looking to tie down a place in the Saddlers' first-team.
The 21-year-old former Republic of Ireland youth international made fifteen first-team appearances during an injury hit 2019/20 and will no doubt be keen to add to that number during the upcoming campaign.
Speaking via the club's official website, Callum said; "I’m obviously delighted and I’m happy to be here. I am looking forward to next season.
"There has been a bit of a break now and I had quite a big injury layoff, so I am really happy to get the new deal sorted and hopefully I can get some game time next season.
"Last season it was a new squad so everyone was getting to know each other and each others games but this season we have keep a nucleus of players.
"We should now know how each other play because we have had near enough a full season together so I am hoping that it is going to be a good season."
Cockerill-Mollett’s last appearance for the Saddlers came back in a League Two clash with Salford City back in January, and, whilst being frustrated with the injury that he picked up, he accepted that these things happen in football and is determined to bouncing back.
Callum continued; "When you train every day and you work really hard to get that opportunity, it is frustrating.
"When you then take that opportunity to become a first team regular, because I managed to get quite a few games on the bounce and then I got injured, it came at a bad time really, I felt like I was just about to hit a good bit of form.
"The timing wasn’t great but these things happen in football and you have just got to get on with it and work hard behind the scenes with the likes of Rev who has really helped me out with going to see the top quality specialists and doctors.
"When I was in the youth team, I did play at left centre half a few times but very rarely. The gaffer saw my defensive qualities last season and thought that I would fit in that role quite well and I actually quite enjoyed it.
"I felt as though it was actually one of my best positions to play in. I would take that as my first position but it is a little easier in a three because there is more cover there for you."