In recent years, poly(N‐isopropylacrylamide)‐based microgels have been emerged as a new thermoresponsive coating for cell/cell sheet harvesting, yet few work reports their effect on cell attachment, morphology, activity, and proliferation in details. In this work, poly(N‐isopropylacrylamide‐co‐styrene) (pNIPAAmSt) microgel was selected as the model to study its density on NIH3T3 cell adhesion, morphology, activity, and detachment. Results showed that 0.5 wt % pNIPAAmSt microgel density leads to more cells adhesion, higher cell activity yet lower cell proliferation. Moreover, cell adhesion location can be well controlled either by manipulating the sub‐cellular scale distances between microgels or by fabricating large scale surface patterns of the microgels on higher microgel density. By temperature stimuli, similar ratio cells detached from the microgel density surface from 0.5 to 1.5 wt %. The results in this article are worthy for the application of thermoresponsive microgels in cell regulation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48773.