We report on a novel microsystem for assessing the effects of tumor treating fields on cancer cells. The platform features at its core an integrated capacitance sensor fabricated in a 0.35 μm CMOS process. The device also includes a cell culture well and miniaturized electrodes for generating arbitrary TTField patterns. The measured capacitance data show a clear distinction between cell cultures treated with TTFields relative to those that remain unexposed. The pro- posed approach provides an inexpensive, real-time, and label-free means to conduct mechanistic TTField studies in vitro.