Dynamical Casimir–Polder force on a partially dressed atom in a cavity comprising a dielectric

•We get the dynamical CP force on a partially dressed atom in a dielectric cavity.•The force in this cavity is larger than that in infinite dielectric space.•The force is not symmetric with respect to the center of the cavity.•The oscillating time of the force increases with the cavity size.

We put a two-level atom into a cavity comprising a dielectric with output coupling. An analytical expression of the dynamical Casimir–Polder force in such a system is obtained when the system starts from a partially dressed state. And the effects of several relevant parameters of the system on the time-dependent force are also discussed.