Moyes has come under increasing pressure during his first season at Old Trafford following a number of disappointing results.
However, Charlton is confident that the Scot will lead the team to success in the coming years.
"It doesn't mean we are going to change everything [overnight]," the 76-year-old is quoted as saying by BBC Sport. "I'm absolutely certain that we picked the right man."
United return to action tonight when they entertain bitter rivals Manchester City in the Premier League.