CCD photometric observations of the near-Earth asteroid 2012 QG42 were made by a collaboration of observers in the U.S. and Europe. The asteroid was found to be a slow rotator, having a synodic period of 24.22 ± 0.01 h based on a data set spanning nearly two weeks. The amplitude of the lightcurve was 1.18 ± 0.03 mag.