The elongated double-fold foldable structural truss has a quadrilateral framework extending along a longitudinal direction. It includes four chord beam units disposed parallel to one another. Each chord beam unit includes two spaced-apart and juxtaposed beams running parallel to one another. The beams define between them a first open channel that is opened on one of the inner sides of the chord beam unit. The structural truss further includes four web units having brace members. The brace members of at least two of the web units are telescopic. The telescopic brace members are all in their extended position when the structural truss is in its unfolded position and being all in their retracted position when the structural truss is in its folded position. The foldable structural truss is very compact in its folded position.