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.