The Sealyham Terrier is one of the calmest in the Terrier Group. Being a terrier means they are lively, energetic, and excitable. But they have many faithful fanciers because these typical terrier traits are tempered by cheerfulness and playfulness. Sealyham Terriers are proud, confident, and courageous. They assume a role of equal footing within their family and demand affection. They are, in return, extremely devoted, lovable, and loyal. They also like to protect their people and make above average watchdogs without being unnecessarily boisterous. However, they should not be relied on to make a good guardian. Once a visitor is welcomed, you can expect them to be accepted well by a Sealyham Terrier. They do best with children who are older and well behaved. As with most terriers, they will not tolerate being teased. They accept or at least put up with both dogs and non-canine pets better than many other terriers but caution is still advised. Requiring little exercise, a Sealyham Terrier can easily live in an apartment. They are fairly calm and even somewhat lazy indoors. More active outside, they like walks, play sessions, or free play time in a yard. If allowed off leash outside, they should be confined to a safe, fenced area. They like an adventure and as a hunting breed will instinctively chase small prey. They also enjoy digging.

Sealyham Terriers are small dogs no more than 10 inches tall and weighing between 18 and 24 pounds. Their harsh wire coat is usually white to yellowish white with gray to blue markings fairly common, especially around the eyes. Their coat should be brushed two to three times a week; their shedding is minimal. Many pet owners opt to have them clipped as show coats are difficult to maintain. They prefer a moderate climate but are able to tolerate any reasonable temperature.

Typical of terriers, a Sealyham Terrier benefits from additional efforts to socialize them. Like the other terrier breeds, they present a challenge to the trainer but are not as difficult as most others in the Terrier Group. As a result of not being as intelligent as some his terrier cousins, they are more likely to focus on their trainer. Still, the most effective training involves games and positive motivation. A Sealyham Terrier may be a good choice for someone interested in a terrier but intimidated by the energy and antics typical of the group. Although the Sealyham may be the calmest of the terriers, they still have the terrier attitude that endears them to a terrier lover. Even though more moderate than many of their brotheren, a Sealyham is not a good choice for a first-time dog owner.