In this paper, we find the necessary and sufficient conditions, inclusion relations for Poisson distribution series K(m, z) = z + ∞ n=2 m n−1 (n−1)! e −m z n belonging to the subclasses S(k, λ) and C(k, λ) of analytic functions with negative coefficients. Further, we consider the integral operator G(m, z) = z 0 F (m,t) t dt belonging to the above classes. Mathematics Subject Classification (2010): 30C45.