The discovery of stimuli‐responsive high affinity host–guest pairs with potential applications under biologically relevant conditions is a challenging goal. This work reports a high‐affinity 1:1 complex formed between cucurbit[8]uril and a water‐soluble photochromic diarylethene derivative. It was found that, by confining the open isomer within the cavity of the receptor, a redshift in the absorption spectrum and an enhancement of the photocyclization quantum yield from Φ=0.04 to Φ=0.32 were induced. This improvement in the photochemical performance enables quantitative photocyclization with visible light that, together with the near‐infrared light‐induced ring‐opening reaction and the 100‐fold selectivity for the closed isomer, confirms this as an outstanding light‐responsive affinity pair.