We obtain the general solution and the generalized Hyers-Ulam-Rassias stability of the mixed type additive, quadratic, and cubic functional equation f ( x + 2 y ) − f ( x − 2 y ) = 2 ( f ( x + y ) − f ( x − y ) ) + 2 f ( 3 y ) − 6 f ( 2 y ) + 6 f ( y ) .