Influencers are defined as independent opinion leaders on social media networks who influence the attitudes of their followers through blogs, tweets and the use of other social media. As a result, influencer marketing has become an integral part of brands' marketing strategies. This book has the overarching goal to examine the impact of influencer marketing on consumer behavior and the resulting business success. The first empirical project explicitly examines the question of which influencer characteristics should be considered in the selection process in order to increase different campaign metrics along the consumer decision journey. Campaign data from several brands is used for the project and is extended with survey data from a large-scale consumer survey. The second empirical project examines how the influencer marketing channel, compared to other firm and consumer activities, affects consumer interest and firm performance. The project uses historical data from one of Europe's largest specialized online retailers and analyzes it in a time series model.