Several recent studies have investigated international differences in advertising practices. Most of these address advertising in general, leaving the transferability of comparative advertising practices largely unexplored. Based on a theoretical framework of consumer skepticism toward novel information, we conducted a cross-national study to examine the effectiveness of comparative ad format and message content advertising executions under conditions of market and sponsor brand novelty, and loyalty toward the comparison brand. Analyses of responses from participants in France, the Netherlands, and the United States indicate that novelty of the brand and novelty of the practice of comparative advertising interact with various ad elements to produce both desirable and undesirable outcomes.