Since the end of 2018, the Transiting Exoplanet Survey Satellite (TESS) provides high-quality space data on stellar photometry to the astronomical community. We present the results of an analysis of TESS photometric data for known slowly rotating, magnetic, chemically peculiar (mCP) stars. In general, mCP stars show an inhomogeneous distribution of elements in their stellar atmospheres that leads to spectroscopic (line profile) and photometric (light curve) variations over the rotation period. In the frame of the oblique magnetic rotator (OMR) model, patches of enhanced chemical abundance on the stellar surface reveal the frequency of stellar rotation. Using this approach, we have compiled a list of slowly rotating mCP stars with rotation periods longer than two days from the analysis of the photometric data provided by TESS for the first eight sectors of observations. Slowly rotating mCP stars usually possess a hydrodynamically stable stellar atmosphere where a magnetic field can amplify the process of atomic diffusion and this leads to the horizontal and vertical stratification of chemical abundances.