Let T be a set of transpositions of the symmetric group S n . The transposition graph Tra(T ) of T is the graph with vertex set {1, 2, . . . , n} and edge set {ij | (i j ) ∈ T }. In this paper it is shown that if n 3, then the automorphism group of the transposition graph Tra(T ) is isomorphic to Aut(S n , T ) = { ∈ Aut(S n ) | T = T } and if T is a minimal generating set of S n then the automorphism group of the Cayley graph Cay(S n , T ) is the semiproduct R(S n ) Aut(S n , T ), where R(S n ) is the right regular representation of S n . As a result, we generalize a theorem of Godsil and Royle [C.D. Godsil, G. Royle, Algebraic Graph Theory, Springer, New York, 2001, p. 53] regarding the automorphism groups of Cayley graphs on S n : if T is a minimal generating set of S n and the automorphism group of the transposition graph Tra(T ) is trivial then the automorphism group of the Cayley graph Cay(S n , T ) is isomorphic to S n .