Novel dual molecular- and ion-recognition responsive poly(N-isopropylacrylamide-co-benzo-12-crown-4-acrylamide) (PNB12C4) linear copolymers with benzo-12-crown-4 (B12C4) as both guest and host units are prepared. The copolymers exhibit highly selective sensitivities toward γ-cyclodextrin (γ-CD) and Na+. The presence of γ-CD induces the lower critical solution temperature (LCST) of PNB12C4 copolymer to shift to a higher value due to the formation of 1:1 γ-CD/B12C4 host-guest inclusion complexes, while Na+ causes a negative shift in LCST due to the formation of 2:1 “sandwich” B12C4/Na+ host-guest complexes. Regardless of the complexation order, when γ-CD and Na+ coexist with PNB12C4, competitive complexation actions of B12C4 as both guest and host units toward γ-CD and Na+ finally form equilibrium 2:2:1 γ-CD/B12C4/Na+ composite complexes, and the final LCST values of PNB12C4 copolymer reach almost the same level. The results provide valuable guidance for designing and applying PNB12C4-based smart materials in various applications.