Add the rinsed red kidney beans, diced ham, bell peppers, onion, celery, and garlic to the slow cooker.
Pour in the chicken broth, then stir in the Cajun seasoning and cayenne pepper until everything is evenly mixed.
Season with salt and black pepper, then give the mixture one more stir.
Cover the slow cooker and cook on low for 8 hours until the beans are soft and the broth has thickened slightly.
Stir the soup once more before serving to distribute the ham and vegetables.