They each picked up a Doctor of Laws degree from the University of St Andrews for their achievements in the sport.
The 38-year-old Irishman won The Open in 2007 at Carnoustie.
In 2008 he defended his Open Championship title at Royal Birkdale and then followed up by winning the US PGA Championship in the same year.
Harrington said: “I’m thrilled with the honour from St Andrews University. I nearly came here to study in 1989 and it’s nice to come full circle, I suppose, and get this honorary doctorate here.
“It was made all the more special with the fact that Arnold Palmer and Tom Watson were there as well, so yeah – very, very important.”
The degrees were presented by university chancellor Sir Menzies Campbell.