With the majority of its occurrences scattered across Latin literature and mostly lacking situational context, the Roman ethical concept of moderatio is hard to grasp in all its facets. Its fundamental meaning appears to have been the reasonable and prudent use of power, but how moderatio was actually manifested in historical action, how it varied and was defined, and who was expected to display it may still be debated. In his Facta et dicta memorabilia, the Tiberian author Valerius Maximus presents a unique and focussed discussion of the nature and the effects of moderatio (Val. Max. 4.1). The exempla he assembles clearly illustrate the patterns and processes which underlie this highly complex mode of conduct. Based on a thorough analysis of these exempla, this article attempts a definition of moderatio as understood by Valerius. Thus the paper seeks to highlight some of the essential aspects shaping this extraordinary virtue, to explore potential intentions behind its display, and to examine its function within the relationship between the powerful and those on whom their power impacted.