A series of responsive polymeric fluorescent sensors (PDSM-PEG-F) were fabricated by post-grafting pyrene and poly(ethylene glycol) onto the backbone of a pseudo-crown ether containing cyclopolymers. These fluorescent sensors exhibited tunable dual-responsiveness towards temperature and pH, and showed good selective recognition toward metal ions above their phase transition temperatures. PDSM1-PEG1-F1 with a small pseudo-crown ether cavity (similar to 15-crown-5) exhibited selective detection towards Cu²⁺ and Ag⁺ at 33 °C, showing detection limits of 1.20 μM and 0.75 μM, respectively, PDSM1-PEG2-F1 and PDSM2-PEG1-F1 towards Fe³⁺ and Ag⁺, and PDSM3-PEG1-F1 towards Na⁺ and Au⁺. This thermo-sensitive controllable selectivity toward metal ions would provide an efficient strategy for fabricating other diverse fluorescent sensors by simply changing the size of the pseudo-crown ether cavities in the cyclopolymers.