Wood, who was one of the iconic figures on both the 1997 Lions tour to South Africa and the 2001 tour to Australia, takes up his position with immediate effect, along with fellow newcomer Nigel Northridge.
"I am absolutely delighted that Keith and Nigel have joined our Board," said London Irish chairman Andrew Coppel.
"They are both passionate about the club and share the Board's ambition to see the club enhance its performance both on and off the field.
"It is a positive reflection on the club that such high calibre individuals are keen to devote their valuable time to our affairs. I have no doubt that they will make a major contribution to the future success of London Irish, complementing the strong qualities of the current Board."
Now 36 and an inductee of the International Hall of Fame, Wood won 58 caps for his country and played five Test matches for the Lions as he became one of the most popular figures in the World game.