A promising starting point
Generally, yes — this is one of the easier giant breeds to combine with cats. The Bernese Mountain Dog's temperament is gentle, patient, and people-and-home oriented rather than prey-driven. Berners were farm dogs who lived alongside other animals, and most adults regard a household cat as part of the furniture: someone to sniff, step around, and occasionally share a warm spot with.
Plenty of Berner owners describe the cat as the household member firmly in charge, with the huge dog politely complying. That outcome is common, but it is earned through sensible introductions rather than assumed on day one.
Where the risks actually sit
The main risk is not aggression. It is physics and excitement. A young Berner playing at full enthusiasm can knock a cat flying without a trace of malice, and an elderly or frail cat is more vulnerable still. The second risk is the chase reflex: even a mild-mannered dog may pursue a cat who suddenly bolts, and a chase that starts as play can frighten or injure the cat at the end of it.
Cats, for their part, vary. A confident cat who stands her ground usually teaches a puppy respect quickly. A timid cat who always runs can keep the chase game rewarding for the dog, so management matters more in timid-cat households.
Introducing them the way that works
Start with scent before sight: swap bedding, feed both animals on opposite sides of a closed door, and let each learn that the other's smell predicts good things. Move to visual contact with the dog on a lead and a barrier between them, rewarding the dog for calm behaviour and for looking away from the cat. Let the cat choose her distance at every stage, with high shelves, baby gates she can slip through, and a room the dog cannot enter.
Short, boring sessions are the goal. If the dog can lie down and ignore the cat for a few minutes, end there and repeat tomorrow. Only when weeks of supervised calm have passed should the pair share a room off-lead, and even then the cat keeps her escape routes permanently.
Puppies, adults, and rescue dogs
A Berner puppy raised with a cat usually grows up entirely relaxed around cats generally, though puppy play needs supervision until the dog learns his own size. An adult rescue Berner's history matters more than the breed label: ask the rescue directly how he behaved with cats in a foster home, and treat an unknown history as a reason for the full slow introduction, not a reason to skip it.
Any dog who fixates on the cat — staring, trembling, unable to respond to you — is telling you the introduction needs to slow down or that the pairing may not be safe, and a behaviourist's input is worth getting early.
Keeping two species' routines straight
A mixed household runs on details — which animal eats where, whose litter area is dog-proof, which doors stay gated. Through KinsLe Family Sharing, the relatives you pick can view your Bernese Mountain Dog's profile for themselves.