  This study aims at timing the eclipses of the binary star TU UMi. The times
of minima are taken from the literature, from our observations in April 2004
and from TESS observations between 2019 and 2022. The orbital period analysis
of the system indicates that there is a cyclic oscillation with an amplitude of
0.0081d and a period of 9.03 yr, accompanied by a continuous decrease at a rate
of $dP/dt =-1.12 \times 10^{-7}\,\mathrm{d}\, \mathrm{yr}^{-1}$. We study the
secular evolution of the orbital period of the system and the possibility of
the existence of a third companion or the magnetic activity cycle of the
primary component in the system.
