Every bounded composition operator C ψ dened by an analytic symbol ψ on the complex plane when acting on generalized Fock spaces F p ϕ , 1 ≤ p ≤ ∞, is power bounded. Mean ergodic and uniformly mean ergodic composition operators on the spaces are characterized. The set of periodic points of these operators is also determined. Theorem 1.1. (Theorem 2.1 of [18], Theorem 2.1 of [19]) Let 1 ≤ p ≤ ∞ and ψ be a nonconstant analytic map on the complex plane C. Then the operator C ψ : F p ϕ → F p ϕ is 1 *Corresponding author Key words and phrases. Composition operators, generalized Fock spaces, power bounded operator, mean ergodic operator, uniformly mean ergodic operator.