Summary: By utilizing the interaction of α‐cyclodextrin (α‐CD) with dodecyl side chains in polymers of x mol‐% dodecyl‐modified poly(acrylic acid) (p(AA/C12(x))), systems that undergo gel‐to‐sol and sol‐to‐gel transitions were successfully constructed. Rheological experiments indicated that addition of α‐CD to the hydrogel of p(AA/C12(5)) caused a drastic decrease in the viscosity, while addition of oligo(α‐CD) to the solution of p(AA/C12(2)) led to a remarkable increase in the viscosity.