Graphene resonators hold a promising potential to be integrated into nanoscale sensors and electronic devices. Therefore, understanding the physics underlying their dissipation mechanisms is essential. Here we investigate the dissipation of graphene through a study of graphene foam (GF) resonators. We show that intrinsic material dissipation, related to interlayer friction, is a primary source of energy dissipation in graphene. We fabricated GFs with varying wall thicknesses and characterized their frequency responses under ambient and vacuum conditions. Additionally, we investigated their atomic structure by using Raman analysis, high-resolution scanning electron microscopy, and transmission electron microscopy. While air losses are considered the primary dissipation source of micro- and nano-electromechanical systems (M/NEMS) operating under ambient conditions, we show that friction between graphene layers is a comparable source for energy dissipation and, thus, it limits the dynamic amplification of multilayer graphene resonators even when they are operated under high-vacuum conditions. We show that the friction between the layers is enhanced when multiple layers exist and that dissipation is further amplified by microscopic defects, such as cracks and grain boundaries, or by the existence of amorphous carbon. Thus, we uncover the fundamental physical behavior of graphene. Display omitted •We study energy dissipation in graphene resonators.•We excited resonators under ambient and vacuum conditions, SEM and TEM analyses.•Layer friction was found to be the main source for energy dissipation.•Grain boundaries, micro-cracks, and amorphous carbon enhance the dissipation.