Give him a retreat room guests do not use
A house party multiplies everything a dog finds hard: strangers arriving in waves, doors opening, music, dropped food and people bending over him with drinks in hand. Set up a retreat room before the first guest arrives, with his bed, water, a chew and familiar bedding, and make it genuinely out of bounds, with a note on the door if that helps guests remember. Settle him there after an early walk and feed, visit him yourself for calm toilet breaks and short check-ins, and let him choose more company only if he is relaxed, the room he would join is quiet, and you can supervise properly. A dog who adores people can still be overwhelmed by hour three, so watch for yawning, lip licking, hiding behind you or taking himself off to his retreat, and treat that choice as the plan working, not as a shame.
Brief the guests as kindly and clearly as the dog
Most party harm to dogs comes from kindness without information. Tell guests on arrival, briefly and cheerfully, not to feed him anything, not to let him out of any door or gate, and where his retreat room is so nobody wanders in looking for a bathroom or a coat. Move handbags, coats with pockets full of sweets or medication, and gift bags off the floor and out of his rooms entirely, because a dog investigating a guest's open bag is a common and preventable accident. Put party food on high surfaces, clear plates promptly into a closed bin, and keep alcohol, grapes, chocolate desserts, coffee and cooked bones from the roast out of every room he can access, including the garden if guests drift outside with plates in the summer.
Run toilet breaks, garden time and bedtime on his clock
Party time and dog time run differently, so schedule his needs rather than hoping to notice them. Take him out on lead at his usual times, through the quietest exit, and stay with him in the garden if guests are outside, since an open gate during a group photo or a delivery is all a loose dog needs. Keep fireworks, party poppers, balloons and sparklers away from him entirely if they feature in the evening, and close windows and curtains if neighbours are celebrating noisily. End his evening at his normal bedtime in his normal sleeping place where possible, with the party kept out of that room, and do a final floor sweep for dropped food, skewers, bottle caps and broken glass before he is allowed to roam the house again the next morning.
Have an exit plan for the dog who should not stay
For a nervous dog, a very young puppy, or a household expecting a loud, crowded night, the kindest plan may be an evening elsewhere with a person he knows well. Arrange that early, pack his food, lead, bedding and any regular care items, and write down his feeding times, walk routine, settling cues and your vet's number rather than relying on a doorstep briefing over the doorbell. If, despite planning, he eats party food, chocolate, grapes or something from a guest's bag during the evening, contact a vet promptly with the packaging and a time, and do not wait for symptoms to settle the question. A clear handover through KinsLe Care Pass gives a trusted sitter temporary, clear access to his routine and key details while you are hosting, so his party night runs on his rules wherever he spends it.