Abstract: A collapsible trailer has a rigid base framework formed from longitudinal members and transverse stringers supporting an axle having wheels. On the framework in a seat support structure having a forward, rearwardly angling arm, and a rearward, forwardly angling bracket that are joined in a T-shaped sleeve assembly that includes a transverse sleeve pivotable on the rear bracket and a longitudinal sleeve that engages the arm in socketed relationship. A turnbuckle tensions the bottom of the seat against the framework to hold the supporting structure at any desired degree of firmness. A rear cargo platform is firmly attached to the framework at its forward end and has a foldable rearward end that rests against the wheel axle when in unfolded position.