Named after its creator’s estate during the late XIX century, the Sealyham Terrier has a unique coat, made by hard and soft hair; otherwise, there is nothing soft about this Terrier, it is a great badger, fox and otter hunter. 
Primarily the Sealyham should seem perfectly balanced, a very determined Terrier, with extraordinary substance. It stands to 31 cm to the withers and the males weigh 9 kg, and the females 8.2 kg (the rising is more important than the weigh). The head is long, wide and potent, perfectly balanced, not coarse. The skull is slightly domed and wide between the ears and moderate stop. The cheekbones are not prominent: the nose is black (not white, cherry or butterfly). The eyes are dark, round, deep and medium sized. The ears are folded on the top of the skull, rounded at the tip, slender, should not appear leathery. Raised, tulip or Hound ears are not desirable. The neck is a good length and scope, muscular and well placed on the shoulders, oblique and not too muscular; strong forelegs, good boned; well descending chest (not low limbed, folded, curved or open elbows). The hindquarters especially potent for the dog’s size are not as long as the forequarters. Hocks well angled and parallel. The body is strong and compact; the upper outline straight. The external coat is long and hard, with a wiry texture; the inner coat is resistant. In color, the Sealyham is completely white or white with lemon colored spots, chestnut (tan) or badger at the head and ears. Black spots or excessive mottled is undesirable.
Energetic and loyal, the Sealyham is an ideal play companion for children, great guardian and competent worker. Bred for hard work badger, fox and other vermin hunting, the Sealyham has a strong chasing and digging instinct, which needs to channel. The current dog is more elegant and easier to see in a rink than chasing badgers. It high energy lever can be more than an elderly person handle.
After eight weeks, the Sealyham weighs between 2.5 and 3.5 kg. The tail is docked to a third or half during the first week. The maximum height is reached around the eighth month; complete maturity is reached between the 12th and 18th month. The future owner should choose a puppy with a solid and white body, free of spots (some spots are acceptable for a company specimen), with dark eyelids, oval dark brown colored eyes, and a medium length back. The head should seem large for the body; limbs should be straight; the tail, implanted aligned with the back and carried high. The coat is smooth after eight weeks, not plush. The Sealyham experiences a gradual hair change around the fourth or fifth month; it is usually around the dentition period. “Stripping” eases the process. The color can lighten during the change, especially if the hair is trimmed. The adolescent can be quite messy while eating, and needs to exercise. After 18 months it can display aggression towards other dogs, but this will pass if properly corrected.
The Sealyham may not alarm the badgers in your neighborhood, but its large dog bark is very effective with possible intruders.
The largest concern for the breeder is the eyes, skin and coat. Retinal dysplasia and luxation, evident at birth, occur in the breed. Congenital retinal dysplasia, usually along with cataracts, will quickly become blindness. There are cases of glaucoma, and it has been proven to be the result of retinal luxation. Most skin and hair problems are allergic reactions. Early detection of allergy type is very important, and prevention includes testing breeding lines, and making sure of an adecquate diet and hair care. Epilepsy and deafness also concern the breeders. Hair care is considerable, since a professional hand is needed.
The owner should commit to devoting at least an hour per week to keep the Sealyham abundant coat. It is definitely not a home decoration, but decidedly an active dog that requires plenty of exercise and play time. The owner should watch for possible back injuries, since even without being prone, it is a low build breed and with a long back, which eases this type of injuries. The Sealyham lives 12 or more years.