The reciprocal product degree distance RDD*(G), which is a weight version of the Harary index defined for a connected graph G as vertex-degree-weighted sum of the reciprocal distances, that is RDD*(G) = 1/2 Su,v∊V(G)dG(u)dG(v)/dG(u,v), where dG(u) denotes the degree of a vertex u in G and dG(u, v) denotes the distance between two vertices u and v in G. In this paper, we obtain an upper bound for reciprocal product degree distance of F-sum of graphs which is defined by Eliasi [4]. [ABSTRACT FROM AUTHOR]