Given a graph , a function having the property that if , then there exist such that or there
exists such that , and if , then there exists such that is called a double Roman dominating function (DRDF). The weight of a DRDF is
the sum , and the minimum among the weights of DRDFs on is the double Roman domination number, , of . In this paper, we study the impact of cartesian product on the double Roman domination number.