Why your cat is busiest when the baby finally sleeps
Cats are crepuscular, which means their natural peaks of activity fall at dusk and dawn rather than in the middle of the day when the house is awake. A cat who naps through the afternoon can be wide awake, hungry for play, and fascinated by the one closed door in the house just as the baby drifts off. Crying, milk smells, and a warm room with a soft crib all draw investigation, and if leaping at the nursery door or meowing outside it quickly brings an adult running, your cat learns that this behaviour summons company. None of this is jealousy in the human sense, but the disruption is real, and exhausted parents need a plan that works without shutting the cat away in a way that creates a second problem of loneliness and yowling elsewhere in the house.
Set the night up before bedtime arrives
The most effective step happens an hour before bed. Play with your cat in a proper hunting-style session, following the movement of a wand toy, letting him catch it several times, and then offer his last small meal of the day. That hunt, catch, eat sequence mirrors his natural cycle and makes sleep far more likely than play alone. Set out a warm bed, water, a clean tray, and one or two silent toys in the room where you would like him to spend the night, ideally well away from the nursery. Fit the nursery with a closed door or a tall, secure screen door that lets air and sound travel but not the cat, and make that boundary permanent rather than occasional, because cats test inconsistent rules far more. Check the latch together as part of the household bedtime round so it never depends on one tired person remembering.
Handling the small hours without rewarding the noise
When he meows or scratches at the nursery door at night, the goal is safety without a party. Check the baby quietly if you need to, but avoid feeding the cat, playing with him, or giving extended stroking in response to the disturbance, since all three teach him the tactic works. If he is shut out and distressed rather than merely curious, a brief calm relocation to his prepared room with his bed and toys is kinder than repeated scolding through the door. During the day, let him explore the nursery with you present while the baby is elsewhere, sniff the furniture, and leave on his own, which reduces its forbidden-room appeal. Never leave a cat unsupervised in a room with a sleeping baby, and keep crib nets or covers out of the plan unless they are designed and fitted for that exact crib, as loose netting is itself a hazard.
A shared routine the whole household can keep
This problem usually improves within a couple of weeks once the pre-bed play, final meal, and door routine happen every single night, so the weak point is consistency between parents, grandparents, and anyone staying over. Write the short routine down where everyone can see it, including who does the evening play session and who checks the nursery door last. Note which nights were quiet and which were not, because the log often reveals that a missed play session or a late visitor predicts a restless cat better than any guesswork. If a grandmother staying over wants to see him for herself, KinsLe Family Sharing lets her open his profile — access you grant only to relatives you pick.