The 87-year-old stage and screen actor has also performed Shakespeare and had leading roles in 1950s British films.
The University of Kent awarded the degree to Sir Donald in a ceremony at Canterbury Cathedral.
After receiving his degree, Plymouth-born Sir Donald said: "I thought they were joking. It's very flattering."
He added: "I am suddenly to be made a doctor. I thought they were going to say 'he's going to be doctored', not quite the same thing."
The University of Kent has also awarded BBC North America editor Mark Mardell with an honorary degree this week and science writer and broadcaster Dr Simon Singh collects one on Thursday.
Sir Donald Sinden, star of TV comedies Two's Company and Never the Twain, has received an honorary degree from the University of Kent.