Self pollination is prevalent among plant species. Self pollination provides plants with reproductive assurance when pollinators are limited and provides a 50% gene transmission advantage. Self pollination, however, reduces genetic variation, increases the expression of deleterious alleles, and typically results in reduced fitness. This fitness reduction is called inbreeding depression. Self pollination may also alter interactions between plants and other species. We investigated the effects of inbreeding on anti-herbivore defense in plants. We tested the hypothesis that inbreeding alters the expression of defensive traits and decreases resistance and tolerance of insect herbivory in the yellow monkeyflower (Mimulus guttatus). We found that self pollination altered the production of defensive traits such as trichomes and altered the tolerance and resistance of this plant to two of its common herbivores (the meadow spittlebug, Philaneus spumarious, and the common buckeye, Junonia coenia). The effects of self pollination on plant defense, however, were not always straight forward: inbred plants were often more resistant to herbivores but less tolerant of herbivore damage. Studies like this provide important insights into the ecological and evolutionary consequences of inbreeding in plants that should be incorporated into the short- and long-term management plans of rare or threatened plants and into models of the evolution of self and outcross mating systems.