Yes: a mouse's happiness comes from mice, not from the household
A fancy mouse can live happily in a home with other kinds of pets, because the company it craves is its own kind's. Fancy mice are deeply social with each other, especially females, who usually live contentedly in groups that groom, nest, and sleep in piles together. Dogs, cats, and other household animals contribute nothing to a mouse except risk, so the arrangement is simple: the mice get a rich enclosure and each other, and the larger pets get kept out. A mouse colony behind glass in a quiet room can be entirely content in a house that also holds a cat, provided the barrier discipline never slips.
The enclosure must be cat-proof in structure, not just in intention
Keeping fancy mice in a home with other pets demands an enclosure a cat cannot defeat. A glass or solid-sided tank with a heavy, fastened mesh lid is the safest form, since a determined cat can hook claws through cage bars and can rock a lightweight cage off a table. Set the enclosure on a low, stable stand, not a high shelf it could be knocked from, in a room whose door can stay shut. Inside, deep bedding, nesting material, tunnels, and a wheel let the mice live busy lives that do not depend on out-of-cage sessions. Check lid fastenings whenever the cage is cleaned, because the day a latch is left loose is the day the cat's patience pays off.
Never stage meetings between mice and larger pets
A fancy mouse should never meet a dog, cat, or other predator pet, even restrained, even briefly, even for a photograph. What looks like curiosity from the larger animal is hunting behaviour at low volume, and what the mouse experiences is terror plus the risk of a fatal grab or a saliva-carrying scratch. Out-of-enclosure time for mice should happen in a playpen or secure bin setup inside a closed room with every other pet elsewhere in the house. If a dog or cat fixates on the mouse room door, treat that as a management problem to solve with distance and doors, not as a desensitisation project involving the mice.
Room placement and the mouse's sense of smell
A fancy mouse reads its world largely through smell and sound, so placement shapes its happiness in a predator's house. A cage parked beside the dog's bed or under the cat's favourite perch bathes the mice in predator scent and thumps, and chronically stressed mice breed poorly, fight more, and hide constantly. Choose a calm room the bigger pets rarely enter, keep the door closed, and let the mice's own colony scent build in their bedding between partial cleans, which comforts them. Their active hours run toward evening and night, so a room that is quiet by day also protects the sleep of the whole group.
Group rules worth agreeing as a household
Most losses of fancy mice in multi-pet homes trace back to people rather than predators: a lid left open during spot-cleaning, a child carrying a mouse through the house past the cat, a playpen session in a room the dog wanders into. Set the household pattern once: mice are handled over their enclosure or playpen, other pets are shut out before any lid opens, and visitors watch through the glass rather than reaching in. Note who feeds and checks water on which days so the colony is never missed. KinsLe's Family Sharing keeps your fancy mice's lid, door, and handling rules plus their feeding rota on one shared profile, so the smallest residents get the same careful consistency as every other pet.