The inverse sum indeg (ISI) index of a graph  is defined as where d_u and d_v are the degrees of the vertices u and v, respectively. In this paper, we study ISI index of some graph operations viz., k-fold, strong double, extended double cover, tensor, Cartesian, corona, subdivision-vertex corona, subdivision-edge corona, subdivision-vertex-neighborhood corona, subdivision-edge-neighborhood corona. In the study, we establish some exact formulas and some bounds on ISI index of the operations. The extremal cases for the bounds are also discussed.

degree of vertex, inverse sum indeg index, operations of graphs.