The interest in asteroids is increasing, due to their promising clues on the origin of the Solar System, e.g. their albedos and sizes can provide insight into the protosolar nebula. The new scientific mission scheduled to launch in 2021, the James Webb Space Telescope (JWST), provides an opportunity for observation of asteroids. In this thesis, the feasibility of using the Mid-Infrared Instrument's (MIRI) imager on the JWST for serendipitous characterization of asteroids is evaluated. The imager and the medium resolution spectrometer (MRS) run simultaneously. When MRS is running, imager data could be used for detection of asteroids in infrared, where the error in size is only 10%, comparing to 100% in optical, because the thermal radiation is independent of the albedo. Combining the optical and infrared, the albedo can be determined. This prospective use is researched by simulating the sensitivity of the imager. A tool, created during this thesis, simulates realistic cases using proposal (GTO 1282) and determines the known asteroids in the field of view (FOV) of the imager. MIRISim, created by the MIRI European Consortium, simulates their signatures. The results show a 4.1% chance of an asteroid appearing in the FOV and a 96.9% detection of such an asteroid. In a typical MIRI observation, exposure time of 488.4 s, with preferred filter F1280W, the imager can detect asteroids bigger than 250 m in diameter and closer than 3 AU. This could lead to a detection of 733 256 yet undetected asteroids and 183 314 currently known asteroids in the lifetime of JWST.