The complete twisted graph of order n, denoted by T n , is a complete simple topological graph with vertices u 1 ; u 2 ;. . .; u n such that two edges u i u j and u i 0 u j 0 cross if and only if i\i 0 \j 0 \j or i 0 \i\j\j 0. The convex geometric complete graph of order n, denoted by G n , is a convex geometric graph with vertices v 1 ; v 2 ;. . .; v n placed counterclockwise, in which every pair of vertices is adjacent. A biplanar tree of order n is a labeled tree with vertex set fv 1 ; v 2 ;. . .; v n g having the property of being planar when embedded in both T n and G n. Given a connected graph G the (combinatorial) tree graph T ðGÞ is the graph whose vertices are the spanning trees of G and two trees P and Q are adjacent in T ðGÞ if there are edges e 2 P and f 2 Q such that Q ¼ P À e þ f. For all positive integers n, we denote by T ðnÞ the graph T ðK n Þ. The biplanar tree graph, BðnÞ, is the subgraph of T ðnÞ induced by the biplanar trees of order n. In this paper we give a characterization of the biplanar trees and we study the structure, the radius and the diameter of the biplanar tree graph.