A radio labeling of a graph G is a function f : V (G) ! f1; 2; : : : ; kg with the property that j f(u)f(v) j 1+diam(G)d(u; v) for every pair of vertices u; v 2 V (G), where diam(G) and d(u; v) are diam- eter and distance between u and v in the graph G respectively. The radio number of a graph G, denoted by rn(G), is the smallest integer k such that G admits a radio labeling. In this paper, we completely determine radio number of all transformation graphs of a path.