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We report on the fabrication of photochromic polymersomes exhibiting photoswitchable and reversible bilayer permeability from newly designed poly(ethylene oxide)-b-PSPA (PEO-b-PSPA) diblock copolymers, where SPA is spiropyran (SP)-based monomer containing a unique carbamate linkage. Upon self-assembling into polymersomes, SP moieties within vesicle bilayers undergo reversible phototriggered isomerization between hydrophobic spiropyran (SP, λ₂ > 450 nm irradiation) and zwitterionic merocyanine (MC, λ₁ < 420 nm irradiation) states. For both SP and MC polymersomes, their microstructures are stabilized by multiple cooperative noncovalent interactions including hydrophobic, hydrogen bonding, π–π stacking, and paired electrostatic (zwitterionic) interactions, with the latter two types being exclusive for MC polymersomes. Control experiments using analogous block copolymers of hydrophobic SP …