Ronaldo scored twice on his second Old Trafford debut on Saturday, helping United to a 4-1 win over Newcastle.
Ferguson was in the crowd watching Ronaldo and it's believed he played a key role in the 36-year-old's transfer.
He spoke to Viaplay prior to kick-off and explained: "I'm as excited as everybody else for Ronaldo's return.
"The anticipation all day, waking up this morning, it's a great day for United."
When asked about his involvement, Ferguson replied: "A lot of people played their part. I contributed knowing that really Cristiano wanted to come here.
"And that was important. It worked very well."
He continued: "I wouldn't say it's emotional but it's certainly exciting and also, relief. A lot of relief. I couldn't imagine him playing for Manchester City.
"That's why we took steps to ensure he came here. The club followed him very well, I spoke to the Glazers and it was done."
Ronaldo touched on Ferguson in his first interview since re-joining and couldn't hold back the love for his 'footballing father'.
"As everybody knows, since I signed for Manchester [United] at 18, Sir Alex Ferguson was the key," he said.
"I remember when we played against Manchester when I was at Sporting Lisbon. For me, Sir Alex Ferguson is like a father in football for me.
"He helped me a lot, he taught me many things, and in my opinion of course he had a big role because the relationship that we had, we keep in touch all the time, and he's an unbelievable person.
"I really like him a lot and he was the main key for me to be in the position that I am, that I signed for Manchester United."
United are currently top of the league after the weekend's results and manager Ole Gunnar Solskjaer couldn't be more delighted.
When discussing Ronaldo, the Norwegian said: "Cristiano was looking forward to this he had a little speech last night to the boys.
"Its about sensing the moment, feeling the danger. He's evolved into a proper team player.
"You've got to be there to score the goals and he knows where the goals are getting scored. Not many in the world who have scored more goals than him.
"Very pleased with him, good work rate, patience, it was never going to be easy."
Featured Image Credit: Viaplay & PA Images
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