Cell-based impedance spectroscopy is a promising label-free method for electrical monitoring of cell activity. Here we present a diamond-based impedance sensor with built-in gold interdigitated electrodes (IDEs) as a promising platform for simultaneous electrical and optical monitoring of adipose-derived stem cells (ASC). The impedance spectra were collected in a wide frequency range (from 100 Hz to 50 kHz) for 27 h of cultivation in chambers designed for static cultivation. Absolute impedance spectra were analyzed in terms of measurement frequencies and cell properties monitored by high-resolution digital camera.