Souttar has already been named in the U21 squad this week, but he could be promoted to the senior group for the friendly against Belgium and the first Nations League game against Albania.
Hearts have made a good start to the Scottish season, sitting top of the table after three wins in their opening three games.
Souttar has played a part in all three victories, and this form will be rewarded by McLeish and could see him fulfil a boyhood dream when he walks out at Hampden Park.
One name not in the squad will be James McArthur, who requested time off from internationals as he manages a back problem.