Scholes, 34, has signed a one-year deal, while Fletcher has committed himself to Old Trafford for a further three seasons.
And this despite the former England star being ruled out for 10 weeks with a knee injury.
"I am very confident Paul will be back," said the United boss.
"He can play for at least another year. I have no fears about that.
"He has the same characteristics as Gary Neville, who has just come back after 18 months out.
"They look after themselves and you have to admire that perseverance and determination."
"Paul has come back repeatedly," added Ferguson.
"He will be working away in the gym so that when he comes back he will be ready.
"He is proof that if you look after yourself you can carry on playing and be rewarded at a club of this size.
"He is 34 now and he has been here since he was 14. That tells you the desire and the ability he has to stay at the top."
24 year old Fletcher is also a one-club man, and has agreed a new contract until June 2012.
"Darren is in the same vein as Paul, Ryan Giggs and Wes Brown in that he is a long-serving member of the team," said Ferguson.
"His consistency and level-headed approach is a great attribute and we are all delighted he has signed a new contract."
Fletcher added: "When you play at such a great club with a great team you always want to be a part of that.
"The spirit here is amazing and I am happy that I can play my part in achieving more success."