Recent advances in understanding kinetically controlled pathway complexity have greatly promoted the precision control of supramolecular polymerization. Among them, seeded living supramolecular polymerization (LSP) has proven highly effective for constructing supramolecular polymers with tailored lengths, dispersities, and sequence-defined structures. However, conventional noncovalent interactions often suffer from intrinsic environmental sensitivity, which compromises the kinetic stabilization of metastable species by prematurely activating dormant conformations, thereby undermining the fidelity and stability of the LSP process. Herein, we report a cation–π interaction–dominated strategy for active control of supramolecular polymerization, in which distinct binding modes are dynamically switched and modulated by reversible photoisomerization of azobenzene. This design enables efficient capture and stabilization of metastable states, offering integrated control over both polymerization kinetics and structural outcome. A model monomer, Trans-M1, was designed with a trans-azobenzene core bearing aromatic cationic and π-units at its termini. Trans-M1 undergoes spontaneous 2D supramolecular polymerization via alternating intermolecular cation–π interactions to form ordered nanosheets (Pathway A). Upon 365 nm light irradiation, the monomer folds into a dormant conformation stabilized by intramolecular cation–π interactions (Pathway B). Subsequent 460 nm irradiation triggers unfolding of the dormant species into active monomers, which bypass the nucleation barrier and initiate rapid LSP when exposed to 2D nanosheet seeds (Pathway C). Additionally, rapid quenching of the Trans-M1 monomer leads to the formation of deeply kinetically trapped one-dimensional (1D) nanofiber aggregates with considerable stability, which do not spontaneously convert into the thermodynamic product over time (Pathway D). This work demonstrates that integrating photoresponsive conformational switching with tunable cation–π binding enables full-pathway regulation of supramolecular polymerization across multiple energy landscapes. The approach establishes a generalizable framework for metastable species control and dynamic structural modulation in functional supramolecular materials.