Ear cleaning using ear cleaners is recommended for the prevention of canine otitis externa. This study aimed to investigate the prevalence of bacterial contamination in home- and clinical-use ear cleaners and identify characteristics associated with such a prevalence. To obtain data regarding home-use ear cleaners, 100 bottles of commercial ear cleaners were collected from clients who visited animal clinics with their dogs and completed a survey. Data for clinic-use ear cleaners were obtained by gathering 60 bottles of ear cleaners from private animal hospitals. Bacterial culture of the applicator tips and samples of the ear cleaners was performed. In addition, to determine the relationship between ear cleaner contamination and otitis externa (OE) in dogs, ear cultures were obtained from some of the dogs that visited the clinics. Approximately 5% and 4.91% of home- and clinic-use ear cleaner applicator tips, respectively, had bacterial contamination, although no contamination of the solution within the bottles was observed. Most of the contaminated ear cleaner tips were unclean on the outside given that the bottle was placed directly into the ear canal. The contamination rate was highest among owners who used ear cleaners once a week and among veterinarians who used the product for dogs with OE. We found no ingredients that affected the incidence of ear cleaner contamination.