Botanical gardens are highly heterogeneous plant systems characterized by high taxonomic diversity, with numerous plant taxa represented within confined areas, and complex ecological interactions that create unique challenges for pest management. Conventional IPM strategies, designed for simplified agroecosystems, often fail to address complex pest pressures in curated environments. Microbial biostimulants have emerged as promising components of sustainable IPM strategies by enhancing plant defense responses, improving stress resilience, and reducing reliance on chemical inputs. This review synthesizes current knowledge on microbial biostimulants, including plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi and endophytic microorganisms, in modulating plant defense against insect herbivores. These beneficial microbes enhance plant resistance through multiple mechanisms. They activate induced systemic resistance and modulate key phytohormones, including jasmonic acid, salicylic acid, and ethylene. Additionally, they regulate calcium-dependent and reactive oxygen species-mediated defenses. Microbially induced changes in plant secondary metabolites and volatile organic compounds further influence herbivore behavior and trophic interactions. Emphasis is placed on integrating microbial biostimulants into IPM frameworks tailored to botanical gardens. This highlights compatibility with biological control agents and reduced reliance on synthetic pesticides. Despite promising advances, challenges remain, including context-dependent efficacy, host specificity and limited long-term validation. Overall, microbial biostimulants offer a promising tool for enhancing IPM in biodiversity-rich botanical gardens, although further long-term validation is needed to fully assess their sustainability and effectiveness.