In search of effective ways to encourage consumers to follow desired behaviors such as healthy eating, recycling, or financial planning, marketers sometimes use praise (e.g., "You are doing great") and sometimes use scolding (e.g., "You are not doing enough"). However, the effectiveness of each approach in triggering behavior is not clear. A possible reason for the mixed results in this area is that it is not only what one says that matters but also how one says it: praising and scolding can be performed with a more or less assertive tone. This research introduces assertiveness as a moderator that can explain when praising or scolding would be more effective. Two field experiments in the context of hand hygiene and financial planning demonstrate that when communicators praise consumers, an assertive tone may be more effective in encouraging behavior, whereas scolding requires a nonassertive tone. The authors then replicate these field findings in a controlled laboratory experiment, which also provides click rates as an actual behavioral outcome.