Endometritis is an important cause of subfertility and infertility in the bitch. The normal canine uterus contains a commensal micro biota; however, disruption of microbial balance or impaired uterine immune function can predispose to inflammation. Unlike metritis, which involves all uterine layers, endometritis is limited to the endometrium and commonly occurs postpartum or following mating. Postpartum endometritis may persist as a clinical or subclinical condition, whereas postmating endometritis results from uterine contamination during breeding combined with inadequate uterine clearance. Persistent inflammation creates a hostile uterine environment that negatively affects sperm survival, fertilization, embryo development, and implantation, ultimately reducing conception rates and litter size. Preventive strategies focus on hygienic breeding and whelping management, although evidence-based non-antimicrobial therapies remain limited. Compared with other domestic species, research on endometritis in the bitch is sparse, highlighting the need for further investigation into its pathogenesis, diagnosis, and targeted treatment strategies.