As at the date of this post, the top article as found by Google tells us that Siamese cats get along famously with other cats. This is an incorrect answer. In respect of this aspect of feline behaviour, Siamese cats are no different from any other domestic cat either purebred or random-bred. An individual Siamese cat might get along with another cat very nicely in a multi-cat home. But they might not get along with a different cat in that home.
It depends
And a different Siamese cat might not get along with any of the cats. It depends upon their individual character. It depends upon how they’ve been socialised. But the underlying character trait of all domestic cats is that they are solitary creatures. They have their home range and they don’t like other cats coming onto their home range which is very compressed for full-time indoor cats in multi-cat homes.
Stuck between solitary and social
But of course, over 10,000 years of domestic cat domestication they’ve become really quite sociable. The domestic cat nowadays is sort of stuck between being a solitary wildcat and a sociable domestic cat. But when you adopt another cat to bring into a home where they are resident cats, you do take a risk on whether they will get along or not.
That risk is the same for all domestic cats. If you look at the character traits of the cat breeds on this website or indeed in a book about the cat breeds, you’d be lucky to see a reference to how they get along with other cats. And if you do see it the author will be guessing.
Usual introductory techniques
You have to be realistic. I am a realist. This is not a fluffy/pink article. It is about what will actually happen.
And if you introduce a Siamese cat into a multi-cat hope you will have to normally employ the usual introductory techniques which essentially means that it should be a gradual introduction. You will do well if all the cats tolerate each other and you will do very well if they get along well.
General Siamese cat temperament
As to the Siamese cat’s general temperament, the first point to make is that the Balinese, the Oriental Shorthair at the Oriental Longhair all have the same character because they are all part of a Siamese cat family.
And the number one character trait for these breeds is that they are “vocal to the point of loudness, and are quite active”. Yes, they are quite vocal and they like to be as close as possible to their owner. The Siamese is known to be perhaps a little bit more intelligent than the average domestic cat which makes them inquisitive and nosy. They like to investigate and comment on everything that their owner does.
You might say that they are demanding cats. But the demands can be easily met. But in being more intelligent they might have more distinct opinions about other cats. This may make them less tolerant of other cats but that is pure speculation.
Conclusion
Just take it from me that a Siamese cat might get along with other cats and they might not. You will have to wait and see but please remember the underlying character trait mentioned above. The key to the answer is in that trait.