The Belfast-born centre-back played 52 times for his country, including a draw with England to qualify for the World Cup, while he also featured in over 400 games for QPR
The former centre-back, who made 52 appearances for his country, most famously as part of the side that drew 0-0 with England in 1985 to qualify for the World Cup finals, collapsed whilst playing golf in the morning.
John O'Neill played alongside the man who coached Glentoran to the Irish League championship in 2009, and reflected on his pleasant memories of 'Big Mac', stating that his personality will be badly missed.
"When he came into the Northern Ireland team he had a cockiness about him, but he carried it so well because out on the pitch he was prepared to listen to the experienced players," O'Neill said according to the BBC.
"He put in a tremendous performance in his debut against Romania and matched it in that second appearance against England at Wembley.
"Alan will be badly missed because he was a character and there are not many of them around these days."
McDonald's brother Roy currently works as goalkeeping coach for Irish Premiership side Crusaders, whose coach Stephen Baxter spoke of his shock and paid tribute to the Northern Irishman.
"I have spoken with Roy and the family is in a complete state of shock. Everyone at Crusaders knows the McDonald family so well, we are devastated.
"Alan always thought of everyone else first - he wanted the best for other people.
"He loved his football and did a tremendous job at Glentoran. It was disappointing how it all ended for him there."
Former Northern Ireland boss Sammy McIlroy, who was also a team-mate and friend of McDonald's added: "I'm shell-shocked. Words can't even enter my head at the moment.
"Forty-eight is so young. Alan was always larger than life - during his career and after.
"I have just spoken to Norman Whiteside and he is devastated."
Belfast-born McDonald, who scored one goal for his country, owned a trophy business in Bangor, Co Down, that used to be owned by international colleague Billy Hamilton.
His club career included over 400 games for current Premier League side QPR, with whom he reached the League Cup final in 1986 but lost to Oxford United, as well as spells at Charlton, and Swindon.
When he finishing playing he went on to become assistant manager of Northern Ireland's Under-21s.