  Weak amenability of discrete groups was introduced by Haagerup and co-authors
in the 1980's. It is an approximation property known to be stable under direct
products and free products. In this paper we show that graph products of weakly
amenable discrete groups are weakly amenable (with Cowling-Haagerup constant
1). Along the way we construct a wall space associated to the word length
structure of a graph product and also give a method for extending completely
bounded functions on discrete groups to a completely bounded function on their
graph product.
