In making online hotel booking decisions, people use consumer ratings as a cue to evaluate previous customers' experiences with the promoted hotel. Currently, hotels' sustainability efforts are an important additional criterion that factors into customers' booking behavior. However, the effectiveness of certifying such efforts with sustainability labels is questionable. An experiment was conducted with 684 participants to examine the effectiveness of two different certification systems beyond the persuasive power of customer ratings. To analyze these effects, a 3 (customer rating: poor vs. mediocre vs. good) × 3 (sustainability level: one vs. two vs. three) × 2 (certification system: label vs. rating pictogram) mixed design was used. The results showed that consumers must be able to understand the informational cues that indicate the level of sustainability if they are to use this information in addition to the valence of the overall customer rating as a decision-making criterion.