Honeydew, a sugary excretion from sap-feeding insects, significantly influences plant-insect interactions. While extensive research has examined honeydew’s composition, regulation, and role in insect-plant relationships, its direct effects on plant physiology and health remain understudied. This review synthesises current knowledge about honeydew-plant interactions, focusing on both beneficial and detrimental effects. Adverse impacts include sooty mold development, increased pathogen susceptibility, and reduced photosynthetic capacity due to surface occlusion. Beneficial effects encompass enhanced flowering, strengthened direct and indirect plant defense mechanisms, and improved soil fertility through indirect pathways. The review analyses the relationship between honeydew composition and its effects on plants, while identifying critical knowledge gaps regarding molecular mechanisms and long-term plant responses. This synthesis provides a foundation for future research on honeydew’s role in plant health and ecological interactions.