The frequency dispersion of the dielectric constant of yttrium (Y)-doped (Ba,Sr)TiO3 thin films (Y-BST) in the high-frequency domain (10 kHz–67 GHz) was investigated. In order to remove the substantial parasitic capacitances, inductances, and resistances from the measured impedance data, test samples, short-circuit standard, and open-circuit standard structures were fabricated and their frequency response was measured. Before removing parasitic components, the measured dielectric response showed a rolloff at approximately 4 GHz. However, after circuit calibration, the dielectric constant was almost constant up to 40 GHz where another rolloff was observed. However, this rolloff was due to the uncompensated small parasitic components. Therefore, the dielectric constant of the Y-BST films (170 with a film thickness of 30 nm) showed small frequency dispersion corresponding to the Curie–von Schweidler dispersion, of which the exponent is −0.0131, up to 40 GHz. Furthermore, the decrease of the capacitance was 17% in the frequency range from 10 kHz to 40 GHz.