Airborne particle sampling is a critical element in the study of indoor air quality. The development of high-efficiency particle sampling systems has been a major area of research in the past few decades. Ideally, airborne particle sampling should be conducted isokinetically, which ensures the representation of the particle concentration and size distribution. Sampling probes designed to obtain isokinetic sampling of non-changing airflows, such as in ducts, have been developed successfully and are widely used in practice. On the other hand, no current design of an isokinetic sampling head, which adjusts itself automatically to a variable airflow, exists. This study presents a prototype of an automatic isokinetic sampler for variable flow velocities. This sampler is capable of automatically adjusting its sampling velocities at the sampling inlet so isokinetic-sampling conditions can be satisfied in real-time and in-situ. The performance of the sampler prototype is evaluated in comparison with isokinetic samplers in a wind tunnel. The authors hypothesize that isokinetic sampling will be the most representative method of air sampling in comparison with existing methods and samplers in use.