The King Charles is a friendly breed, to the extent that it is not typically as suitable as a watchdog as some breeds, though it may still bark to warn its owners of an approaching visitor. It is not a high energy breed, and enjoys the company of family members, being primarily a lapdog. Although able to bond well with children and tolerant of them, it will not accept rough handling. It prefers not to be left alone for long periods. Known as one of the quietest toy breeds, it is suitable for apartment living.

This breed can tolerate other pets well, although the King Charles still has the hunting instincts of its ancestors and may not always be friendly towards smaller animals. It is intelligent enough to be used for obedience work and, due to its stable temperament, it can be a successful therapy dog for hospitals and nursing homes.

Whilst the King Charles spaniels' name indicates a very British history – and this is certainly true of their modern history – the first dogs that founded the modern breed actually hail from much further afield. Toy dogs from Japan and other countries in the Far East are generally recognized as the breed's founders. They were initially brought to the UK as diplomatic gifts to the royal houses of Europe as far back as the 15th and 16th centuries. Paintings dating from the early 16th century show small red and white spaniels with petite, short muzzles and high skulls that lived in Italy, and it is likely that these dogs were then crossed with other oriental breeds as well as local Maltese dogs too. Even before the breed became famous under the reign of King Charles, Queen Mary I and also other, later British royalty already owned small toy spaniels, as did many prominent members of royalty on the European mainland.