A graph G of order n is called arbitrarily partitionable (AP, for short) if, for every sequence τ=(n₁,…,n_k) of positive integers that sum up to n, there exists a partition (V₁,…,V_k) of the vertex set V(G) such that each set V_i induces a connected subgraph of order n_i. A graph G is called AP+1 if, given a vertex u∈V(G) and an index q∈ {1,…,k}, such a partition exists with u∈V_q. We consider the Cartesian product of AP graphs. We prove that if G is AP+1 and H is traceable, then the Cartesian product G□ H is AP+1. We also prove that G□H is AP, whenever G and H are AP and the order of one of them is not greater than four.