The particle-free conditions provided by cleanrooms are vital for much of modem manufacturing industry. There has been a substantial increase in the working environment of cleanroom. Special garments are therefore dressed in all cleanrooms to control particles and microbiological contamination dispersed from personnel in cleanrooms. However, more tightly-woven fabrics of cleanroom garments will result in thermal comfort dissatisfaction. In this study, field tests of a cleanroom have been carried out in our newly constructed MEMS laboratory. The ASHRAE thermal comfort code was conducted to investigate thermal comfort of personnel based on field-testing data consequently. Furthermore, the effects of clothing on thermal comfort and contamination control have been assessed comprehensively. The results from computer simulation and field tests indicated that there existed optimum compromise between the predicted mean vote and airborne particle counts under different cleanroom garments. It was also expected that contamination control could be achieved by proper cleanroom garments without the sacrifice of thermal comfort.