Molecular metal-organic cages (MOCs) are constructed via coordination among diverse ligands and metal acceptors with great control over the size, shape, cavity, and composition. Their unique and complex molecular structures make different types of intermolecular interactions, including electrostatic, hydrophobic, hydrogen bonding, van der Waals, π-π and host-guest interactions etc., possible to co-exist in MOC solution. The cooperative or competitive interplay of multiple attractive forces is the driving force leading to exciting and rich solution self-assembly behavior of the MOCs into various supramolecular structures, such as micelles, fibers, nanosheets, nanocubes, nanorods, and blackberry structures. Extensive efforts have been made for gaining better understanding on the formation of these higher ordered structures and designing supramolecular structures with desired properties and functions. In this review, we try to sort out the self-assembly behaviors in MOC solutions from literature based on the type of physical forces involved.