The basic response ability of an array sensor based on plasma-deposited organic film-coated quartz crystal resonators (QCRs) was investigated with a view to their use for indoor air monitoring. The array of plasma-deposited organic film-coated QCRs was applied to detect and separate volatile organic compounds (VOCs) including alkanes, aromatic carbons, chlorocarbons, ketones, and alcohols. Continuous monitoring tests were tried in a real room environment (a refreshment area and a smoking area) with an array of plasma-deposited organic film-coated QCRs along with commercial sensors for indoor monitoring, a relative humidity/temperature sensor, a carbon dioxide sensor, and a three-dimensional micro-ultrasonic airflow meter. To provide a comparison commercial VOC detectors based on a photo-ionization detector and a semiconductor for indoor monitoring tests were used. The plasma-deposited organic film-coated QCRs exhibited fast pulse responses to volatile compounds in the room air along the baseline shift correlated with relative humidity changes and more sensitive responses compared with commercial organic gas detectors.