Montgomery also played American football in his native Scotland, having spent eleven years with Glasgow Diamonds.

[10] Montgomery qualified for the 2006 BDO World Championships along with players like Brian Woods and eventual champion Jelle Klaasen of the Netherlands.

He played in the 2007 International Darts League, beating PDC player Chris Mason, Belgium's Dirk Hespeels and avenged his Lakeside defeat by van der Voort to win Group 4 with a 100% record.

On 26 July 2008 Montgomery won his second event of the year, winning the British Classic, again beating Anderson in the final.

He entered the tournament the following year as the Number 6 seed, but wasted six darts to win his first round match and lost to Garry Thompson.

Montgomery won the 2010 British Classic as well as the 2010 Zuiderduin Masters, his inaugural major title, where he came from 4–0 down in sets to win 5–4 against Robbie Green, also surviving three match darts.

Montgomery showed good form to lift the Dutch Open with victory over Scott Waites and then reach the final of the newly reinstated BDO World Trophy, where he was defeated 13–11 by James Wilson.

At the 2015 World Championship, Monty defeated Pip Blackwell 3–1 in the first round, before dispatching Scott Waites 4–0 in the second to reach the quarter-finals at Lakeside for the first time in his career.

While Montgomery played American football for the Glasgow Diamonds he met his wife Dorothy, who was a cheerleader for the team at the time.