Abstract: A modular frame for seats or furnishing elements provided with a supporting surface includes a plurality of section bars that are adapted to be rigidly constrained to one another so as to define the frame of the supporting surface. The cross section of the section bars is at least partially hollow and substantially triangular and is provided with an opening configured to allow a conveniently shaped terminal part of fixing elements to be longitudinally inserted in the section bar in order to join at least two section bars.