AbstractMulti-wavelength photometry of early-type galaxies (ETGs) in the COSMOS survey is used to demonstrate that the low-level star formation activity in the ETG population at late epochs (z < 1) is likely to be driven by repeated minor mergers. While relaxed ETGs are almost entirely contained within the UV red sequence, their morphologically disturbed counterparts are largely found in the blue cloud, regardless of luminosity. Since empirically determined major-merger rates in the redshift range z < 1 are a few factors too low to account for the number fraction of disturbed ETGs, this suggests that minor mergers are the principal mechanism that drives star formation activity in ETGs at low and intermediate redshift.