The 48-year-old, who earned 40 caps for the Scottish team during his playing career, will work alongside new permanent manager Gordon Strachan.
"I am thrilled to have been asked by Gordon Strachan to join his backroom team," said McCall. "Playing for my country was the highlight of my career and I have been fortunate enough to enjoy World Cup and European Championship finals as a player.
"They hold special memories for me and the Scotland supporters deserve a return to those days. I am proud to be asked to assist with the national team."
Strachan added: "In many ways Stuart typified the classic Scotland international player. He was passionate and combative but he was also hugely influential and inspirational. He has done a tremendous job at Motherwell and his knowledge of the game, and especially his knowledge of the Scottish scene, will be invaluable."