Ferns were among the first broadleaved plants in the fossil record. We assessed fern-arthropod interactions in modern ferns (Monilophyta) as a model for comparison with damage on ferns in the fossil record. We found that the functional feeding groups of margin feeding, hole feeding, surface feeding, piercing and sucking, oviposition, mining, and galling was present on 13 species of ferns at elevations ranging from 750 to 900 meters along mountain slopes of the Brazilian Atlantic Rainforest. We recognized 17 damage types (DTs), including one new DT, and provide implications for interpreting damage on leaves in the fossil record. Nine fossil DTs with modern analogues were found on ferns. Evaluation of damage on modern ferns demonstrate that the variation in the abundance and damage signatures of external feeding, piercing and sucking, galling, and mining enhances understanding of damage patterns on fossil leaves. The taphonomic implications to fossil plant-insect interactions are provided based on the sampling of modern arthropod damage and the preservation biases on ferns. Arthropod remains that are poorly attached to ferns, such as silk webs, eggs, and spider egg sacs, as well as insect exuviae, pupae, and body parts, might provide an important feature for arthropod preservation associated with fern leaves in the plant fossil record. This integrative method demonstrates that DT signatures on modern ferns indicate that ferns are an important host plant for herbivorous arthropods. Consequently, the same importance of ferns as host plants of arthropod herbivores likely was present in deep time.