Inflammatory bowel disease (IBD) is a chronic, relapsing inflammatory disorder of the gastrointestinal tract with increasing global prevalence. Conventional therapeutic strategies are limited by suboptimal efficacy, systemic side effects, and poor patient compliance, while current diagnostic approaches lack sufficient sensitivity and specificity. The advent of nanotechnology, particularly poly(lactic-co-glycolic acid) (PLGA)-based nanomedicine, offers promising avenues for both the diagnosis and treatment of IBD. PLGA nanomedicine exhibits excellent biocompatibility, biodegradability, and controlled drug release properties, enabling targeted and efficient therapeutic delivery. This review comprehensively summarizes recent advances in PLGA-based nanocarriers for IBD management, focusing on innovative design strategies including core-shell architectures, multi-targeting approaches, immune modulation, stimuli-responsive systems, and combination therapies. We also discuss mechanisms to overcome gastrointestinal barriers, enhance mucosal penetration, and modulate the gut immune microenvironment. Furthermore, the integration of diagnostic imaging with therapeutic modalities improves precision in IBD diagnosis. Despite challenges related to long-term safety, large-scale manufacturing, and clinical translation, PLGA nanomedicine holds significant potential for personalized, multidisciplinary IBD treatment, positioning itself as a transformative solution in the field.