This paper considers Grotius's emendations to the text of Tacitus in his 1640 Notae et emendationes, with a particular emphasis on those passages in which Grotius has made a lasting contribution to our understanding of the ancient author: An. 1.32.3, 6.3.1, 11.14.3, 15.47.1, H. 2.1.2, Ag. 10.5, 46.2. It also argues that in four further passages (An. 3.54.6, 12.37.2, 13.46.3, 16.26.2) his contribution deserves to loom a little larger in the text, or at least in the apparatus criticus, of Tacitus's works than it presently does. These emendations are a valuable indication of Grotius's close engagement with the text of an author whose style he aims to reproduce in his own historical writings.