McDonald, 24, who signed from Motherwell in the summer, is Celtic's top scorer with eight goals this term.
"The award means a lot to me. I don't think too many people expected me to play as many games. I've proved a lot of critics wrong," said McDonald.
The striker was instrumental in helping Celtic progress to the group stages of the Champions League and scored the winner in the 2-1 victory over AC Milan.
"I've always had belief in myself. I believe I can play at the highest level and hopefully there is more to come from me," he added.
"I knew it was going to be tough but there was never a doubt in my mind that I could play here.
"You will always have people that will not back you, no matter where you are so it's always nice to shut those critics up."
