The guinea pig (Cavia porcellus) is commonly used in otological research due to its auditory system’s similarity to humans, and it is now also a frequent companion animal seen by veterinarians. Bacterial otitis is the main ear disorder in guinea pigs, though less common than in rabbits. Otitis externa (OE) is inflammation of the external ear canal, often triggered by moisture, trauma (e.g., bites), or parasitic/dermatophytic disease. It is relatively rare and often mild in pet guinea pigs. Diagnosis relies on history, otoscopy, and cytology; treatment includes targeted antimicrobials, antifungals, or antiparasitics, plus NSAIDs and correction of predisposing factors. Otitis media (OM) and otitis interna (OI) are the most frequent ear diseases, usually bacterial (e.g., Streptococcus zooepidemicus, S. pneumoniae, Bordetella bronchiseptica). OM causes exudate, facial nerve paralysis, and systemic signs; OI adds peripheral vestibular signs (head tilt, circling, nystagmus). Diagnosis requires imaging (CT is gold standard) and culture. Medical therapy (antibiotics, anti inflammatories, analgesia) is often insufficient. Surgical options include total ear canal ablation with lateral bulla osteotomy (TECALBO), which carries high morbidity, or endoscopic myringotomy, a less invasive technique for collecting samples and lavaging the bulla but contraindicated if there is osteolysis. The aim of this masterclass is to give an update on how to manage ear disease in guinea pigs and will be the synthesis of 10 years of clinical experience but also original retrospective results including epidemiological data, clinical signs, diagnostics including a CT scan grading system, treatment and outcome.