In this paper we present time-series low-resolution spectroscopy of the pulsating sdB star PG 1325+101, obtained with the Nordic Optical Telescope. We have cross-correlated the spectra and Fourier analysed the variations in radial velocity and the width of the cross-correlation function. From both resulting periodograms we easily recover the known main pulsation period. Further analysis of the spectra, after binning them in phase according to the pulsation period, clearly shows evidence for line-profile variations consistent with a radial pulsation mode. The variations show up in all Balmer and several helium lines sampled by the spectra, and can be understood in terms of temperature, gravity and radial-velocity variations. To the best of our knowledge PG 1325+101 is the faintest object in which line-profile variations due to pulsational instability have been detected so far.