In this paper, we acquire the general solution of the generalized quadratic functional equation
Sigma(1 ˂= a ˂= b ˂= c ˂= m) phi(r(a) + r(b) + r(c)) = (m - 2) Sigma(1 ˂= a ˂= b ˂= m) phi(r(a) + r(b))
-(m(2) - 3m + 2/2) Sigma(m)(a=1) phi(r(a)) + phi(-r(a))/2
where in m ˃= 3 is an integer. We also investigate Hyers-Ulam stability results by means of using alternative fixed point theorem for this generalized quadratic functional equation.