The fabrication of cell sheets is a major requirement for bottom-up tissue engineering purposes (e.g., cell sheet engineering) and regenerative medicine. Employing thermoresponsive polymer coatings as tissue culture substrates allows for the mild, temperature-triggered detachment of intact cell sheets along with their extracellular matrix (ECM). It has been shown before that biocompatible, thermoresponsive poly­(glycidyl ether) monolayers on gold substrates can be utilized to harvest confluent cell sheets by simply reducing the temperature to 20 °C. Herein, we report on the first poly­(glycidyl ether)-based coating on an application-relevant tissue culture plastic substrate. We devised a simple, substrate-geometry-independent method to functionalize polystyrene (PS) surfaces from dilute ethanolic solution via the physical adsorption process of a thermoresponsive poly­(glycidyl ether) block copolymer (PGE) bearing a short, hydrophobic, and photoreactive benzophenone (BP) anchor block. Subsequently, the PGE-coated PS is UV-irradiated for covalent photoimmobilization of the polymer on the PS substrate. Online monitoring of the adsorption process via QCM-D measurements and detailed characterization of the resulting coatings via AFM, ellipsometry, and water contact angle (CA) measurements revealed the formation of an ultrathin PGE layer with an average dry thickness of 0.7 ± 0.1 nm. Adhesion and proliferation of human dermal fibroblasts on PGE-coated PS and tissue culture PS (TCPS) were comparable. For temperature-triggered detachment, fibroblasts were cultured in PGE-coated PS culture dishes at 37 °C for 24 h until they reached confluency. Intact cell sheets could be harvested from the thermoresponsive substrates within 51 ± 17 min upon cooling to 20 °C, whereas sheets could not be harvested from uncoated PS and TCPS control dishes. Live/dead staining and flow cytometry affirmed a high viability of the fibroblasts within the cell sheets. Hence, ultrathin layers of thermoresponsive poly­(glycidyl ether)­s on hydrophobic PS substrates are functional coatings for cell sheet fabrication.