The Spanish Mastiff (also called the Mastin de Espanol) is recognized by the F.C.I. and the Kennel Club of Great Britain. At the present time there is an active parent club in the United States which is working towards recognition of the breed in the Foundation Stud Service. The Foundation Stud Service has several requirements for membership and this breed does not yet qualify. He is being promoted as a guard dog and companion of exceptional gentleness and strong working ability. He is popular at European dog shows but is not often found as a pet except in his native country.

As the name would imply, the dog is a native of Spain and is of the Mastiff origin. He is used extensively still in many parts of Spain as a guard of cattle and sheep and protector of both farmsteads and urban properties. He is noted for his gentle manner and even temper with children in particular and is loyal and affectionate towards his human family and strangers who are welcomed by his master. He will not tolerate visitors who are not invited and is prone to aggression with other dogs. He is very good with livestock and farm animals, treating them in a protective manner and being highly aggressive towards predators. He should be socialized early with his human family. He is quite happy as an outdoor dog and if kept inside he should have access to a large fenced in yard or long walks with his master daily.

The Spanish Mastiff is a large mastiff type breed. His body is longer than it is tall with a good length of leg and a deep chest and body. He has the typical dewlap associated with the Mastiff breeds and the large head with a very deep muzzle. The dewlap is the fold or folds of loosely hanging skin beneath the chin and draping over the top of the chest. The dewlap functions as a deterrent to predators who are not able to sink their teeth into this most vulnerable portion of the body and is present on nearly all of the breeds of dogs who carry out the work of guarding flocks against predators.

The deepness of the muzzle is usually accompanied by loose folds of the lip which are typical also of the mastiff head and usually cause drooling. He has a medium short and very dense coat, usually brindle but may be fawn or lemon and white, black and white, or wolf gray. His coat provides protection against extremes of weather. The long tail is densely furred and quite thick and heavy. It used to be the fashion to crop the ears and the tail also, but now in modern times all "cropping" is frowned upon and his short ears are kept uncropped so they hang in a loosely folded fashion and his tail complements the lines of the body quite beautifully.. He is a large and heavy dog, standing over 30 inches at the shoulder and weighing on average 115-135 pounds.