Initially spaniels in England were divided among land and water spaniels; The English Cocker is one of the oldest types of land spaniel and can be traced back to 14th century Spain. Spaniel type dogs have been found in art and literature for around 500 years and prior to 1600 all types of spaniel were categorised together, the larger ones were used to spring game and the smaller ones to flush out woodcock. This is where the name Springer and Cocker came from when the differentiation among spaniels occurred in the mid 1800's. The rural sports encyclopaedia states that cockers were between 12 and 20 lb and it was not unusual for Cockers and Springers to come from the same litter. In the 1930's the cocker spaniel was the most popular breed in Britain and stayed there for nearly 20 years.

In America a different kind of Cocker was being bred from the English breeding stock which led the kennel club to separate the English and American breeds in 1946. There have also been records of Welsh and Devonshire Cockers. When showing, Cockers and Springers were in the same class until breed standards for the two variants were established in 1885 and since then enthusiasts have bred the individual traits which today differ in more ways than weight alone.

The Cocker breed has some genetic lines which focus on working dogs and others which produce show dogs. After World War II the show bred Cocker became the most popular registered breed but it became popular opinion that they were all useless as working dogs. Of course this was not true and today the Cocker is a popular hunting and working dog, they are highly intelligent and are easily trained and eager to learn. Cuban authorities train and use English Cocker Spaniels as sniffer dogs to check for drugs or food products in passengers' baggage at Cuban airports.

The dogs bred for working have shorter coats and ears which are not desirable for show dogs and although they are registered as the same breed the two strains are rarely crossed due to the significant differences. The working dogs would not win in the show ring and the long coat and ears of the show dog would impede a working dog. The working dogs tails is usually docked at about 4 of 5 inches but a show dogs is docked much closer to the body. Show dogs are restricted to certain colours and white is restricted only to the chest, but workers are a wide variety of colours and some hunters prefer white in the coat to make the dog more visible to the gunners.

A working Cocker Spaniel is a flushing dog and must learn certain skills to do this job efficiently: