The proliferation of advertising in all communication media causes consumers to perceive a significant amount of competitiveness between advertised products, as well as to feel overwhelmed by the intrusiveness of their advertisements. When taken together, these dimensions form the concept ''advertising clutter.'' A review of the literature shows that perceived intrusiveness is the main component of the perception of clutter. Advertising clutter can prompt undesired behaviors (e.g., advertising avoidance) as well as attitudes contrary to those that companies' advertising campaigns hope to achieve. It also leads to diminished advertising efficacy in terms of consumer memory, a decrease in positive attitudes towards the message and brand, as well as declined purchasing intention and, therefore, sales. In this article, the main consequences of advertising clutter for consumers in online media are reviewed and discussed. To that end, a theoretical review of this concept and its main dimensions is performed; special attention is paid to the online context. Finally, some practical recommendations and research opportunities are pointed out.