Research on the 3D culturing of cancer cells that better mimic in vivo solid tumors is important for efficient drug screening. Herein, a new platform that effectively facilitates the formation of cancer spheroids for anticancer drug screening is reported. Cytophilic graphene oxide (GO), when selectively coated on the sidewalls of micro‐wells fabricated from a cell‐adhesion‐resistive polymer, is found to efficiently initiates distinct donut‐like formation of cancer cell spheroids. Scanning electron microscopy and Raman mapping are used to analyze vertically coated GO micropatterns (vGO‐MPs) of different sizes (100–250 µm) on polymer platforms, and human liver cancer cells (HepG2), as a model cancer, are seeded on these platforms. Remarkably, the 150 µm‐sized platform is found to easily and rapidly generate 3D spheroids in the absence of cell‐adhesion proteins. In addition, owing to the unique characteristics of GO, vGO‐MPs are highly stable for long periods of time (≈1 month), even under harsh conditions (>70 °C). Moreover, the anticancer effects of two drugs (hydroxyurea and cisplatin) and the potential anticancer compound (curcumin) on HepG2 cells are demonstrated by simply measuring decreases in spheroid sizes. Hence, this new platform is highly promising as a cancer spheroid‐forming material for rapid drug screening.