Killa, as he is known, began his career with Burnley where he graduated through their youth system. He was tipped to take over their number one goalkeeper at the time Paul Crichton but this wasn't to be and he was loaned out to Lincoln City in September 2000. During his time at Sincil Bank he didn't make a single appearance for The Imps and returned to Burnley in November.

He gave up hope of claiming a place in the starting eleven at Burnley and signed for Halifax Town on a free transfer in February 2001 in an attempt to gain regular first team football. His time at Halifax didn't go as well as he would have hoped as he failed to impress at The Shay and was released on a free transfer in the Summer.

Mawson then made the move to Morecambe and played in a number of pre season matches where he made a huge impression with the Morecambe management and fans. His performances in those pre season games persuaded Jim Harvey to sign him onto a contract and he immediately became first choice ahead of Mark Smith.

His competitive debut came against Nuneaton Borough on the opening day of the 2001/2002 season and he managed to keep a clean sheet to mark an impressive first appearance in a Morecambe shirt. His first season at the club was to be a succesful one for Mawson as he helped the team achieve a 6th place finish in the Nationwide Conference and reach the semi final of the FA Trophy where they were knocked out by Stevenage Borough.

He also began making a name for himself as one of the best young goalkeepers in non league football with a number of impressive performances in important games. Morecambe saw themselves drawn away to Harrogate Railway Athletic in the FA Cup fourth qualifying round and it was mainly down to Mawson that Morecambe didn't find themselves on the end of an embarrasing defeat to the Yorkshire minnows. Morecambe went on to win the game 3-2 and were drawn away to Brentford in the first round in a game that the Shrimps were unlucky to lose 1-0 against the second division side.

The 2002/2003 season saw Craig Mawson continue in between the sticks for Morecambe and he played every game in the clubs league campaign that saw them set a record for highest ever league position. Morecambe's second place finish meant that they took part in the inaugral Conference playoff's where they were drawn against Dagenham & Redbridge. With the tie ending 3-3 on aggregate after extra time at Christie Park the game went to penalties and Dagenham took a 2-0 lead after the first two rounds of kicks. With Dagenham only one goal away from booking a place in the final Mawson produced two excellent saves to allow Morecambe to draw level at 2-2. Unfortunately Jamie Murphy missed the decisive spot kick and Morecambe were knocked out despite Mawson's heroics during the shootout.

Mawson also achieved international recognition that season as he was called up to the England National Game squad but he never got the chance to represent his country as the Conference managers decided that the domestic schedule was too congested to fit in an international match at that time.

To cap a highly successful season for the goalkeeper he was voted as the supporters player of the year for the 2002/2003 season.

Unfortunately for Mawson the following campaign wasn't to be as successful. As the teams form suffered so did his and Mawson found himself making a number of individual errors that cost Morecambe goals and points. Despite this he still remained a firm fan favourite and continued as number one goalkeeper until late February when Mawson picked up his first injury in his three years at Christie Park.

With no other senior goalkeeper on the books Ian Dunbavin was brought in on loan from Shrewsbury Town but his performances weren't enough to keep Mawson out of the side upon his return from injury. Craig ended the season as first choice goalkeeper but he was unable to agree terms over a new contract with Morecambe Football Club and he departed to be replaced by Adam Sollitt.