Your Toddler Keeps Hitting the New Baby. Here’s Why Nothing You’ve Tried Is Working.

You have become a bodyguard. You wear the baby in a wrap most of the day because that’s the only place she’s definitely safe. You’ve built a blocked-off corner of the dining room. You’ve learned to sit with your body between them, and to catch a small hand mid-air, and then catch the other one.

And you have done everything. The book about hands not being for hitting. The one-on-one time. The firm no. The praise when he’s gentle, which he can be, which is the maddening part, because he knows how. He has stroked her hair. Then he tries to hit her.

It’s getting worse, not better. And somewhere around week nine you started wondering, quietly, whether something is wrong with your child.

Why the advice you’re reading contradicts itself

Search this at midnight and you’ll find two camps yelling past each other. One says you have no consequences, use a time-out, remove the toy, remove the fun. The other says time-outs don’t work at that age, he isn’t giving you a hard time, he’s having one, stay calm, stay neutral.

Read enough of those threads and you notice something: the parents asking have already tried the whole gentle list. They aren’t lazy or harsh. They’re paralysed, because two confident groups of strangers are telling them opposite things, and the baby is getting hit while they decide who’s right.

Here’s the resolution nobody offers. They’re answering different questions. The gentle camp explains the why: he’s grieving, he’s flooded, he has no language for it. The consequences camp answers the what: what happens in the two seconds after the hit. You need both. Understanding why he does it is not a plan, and a punishment that ignores why he does it won’t survive the week.

What it actually feels like from his side

Adele Faber↗ and Elaine Mazlish open Siblings Without Rivalry by asking parents to imagine their spouse putting an arm around them and saying:

Then the new wife arrives. She’s smaller and everyone exclaims over her. She gets your clothes. When you object, you’re told to be kind, she’s only little. That’s the deal your toddler was handed, without a vote, by the two people he trusts most. He isn’t being wicked. He’s being replaced, and he has about forty words to say so.

This is also why the regression comes as a package. If potty training has gone backwards at the same time, that isn’t a coincidence, it’s the same signal in a different language, which we unpack in the piece on regression as information.

The part almost nobody says out loud: the hit is working

The American Academy of Pediatrics’ guidance on aggressive behaviour and the best-evidenced approach to toddler behaviour, Alan Kazdin’s Parent Management Training at Yale, land on the same uncomfortable mechanic: attention reinforces behaviour, and it doesn’t much care whether the attention is warm or furious.

So picture what your toddler sees. He raises a hand. Instantly: your eyes lock onto him. Your voice changes. You say his name. You pick the baby up, you make a show of comforting her, you leave the room. From his side, that hit just produced the single most dramatic, undivided reaction he gets all day, plus it removed the competition from the room.

It worked. Of course he’s doing it again in two minutes.

The one change most parents miss

When he hits, you almost certainly pick up the baby and leave. Do the opposite. Remove him, not her.

It sounds like a technicality. It isn’t. If leaving with the baby is the consequence, then hitting reliably gets him a big reaction and gets the baby taken away, which is roughly what he wanted. If he is the one who calmly, wordlessly leaves the fun for two minutes, the equation flips: hitting costs him the room.

Pair it with what Kazdin calls the positive opposite. Don’t just suppress hitting, actively catch and name the behaviour you want, with real specificity, several times a day: not a vague “good boy”, but “you touched her so gently on her foot, look, she’s watching you.” That’s the behaviour you’re trying to grow. Praise is the water.

What actually works, in the order that matters

• Act, don’t lecture. Two flat words, no eye contact, no speech: “no hitting”, then remove him. The talk can happen later, calmly, when nobody’s flooded. In the moment, words are attention.
• Make it instant and small. Two minutes. Every single time, boringly, the same way. Consistency is doing more work here than severity ever will.
• Give the feeling a mouth. He can’t say “I feel replaced.” So say it for him: “You wish Mummy could put her down. That’s a horrible feeling.” Then teach the exit line he can actually use, “space from baby”, and honour it instantly when he says it.
• Make the baby wait, in front of him. Once a day, out loud: “One minute, baby, I’m helping your brother with his shoes.” He has heard the reverse fifty times. Let him hear it land his way.
• Stop forcing the relationship. If every interaction is you asking him to fetch a nappy, being helpful becomes another thing the baby costs him. Drop it for a fortnight. Then rebuild it sideways: she smiles when he dances, she watches him build, she likes his noise.
• Give the aggression somewhere legal to go. A doll he’s allowed to be rough with, a cushion, a wall to high-five. The urge is real; it needs an address that isn’t his sister.

The thing the exhausted threads get right

Sift through enough of these late-night posts and one pattern repeats more than any other: the parents who are a year or two further along almost all come back to say the same thing. It stopped. Often quite suddenly. The three-year-old who couldn’t be left in a room with the baby is now five, and they’re inseparable, and the whole grim season has become a story.

That’s true, and on its own it’s useless when you’re the one in week nine with a bruise on your baby’s head. So take it as the horizon, not the plan. The plan is the boring two minutes, the named feeling, the specific praise. The horizon is that this genuinely, reliably ends.

You’re not failing. You’re outnumbered.

The guilt in this is double, and nobody warns you about the second half. You feel guilty toward your toddler for the world you upended. Then you feel guilty toward the baby, who is spending her first months being fed, put down, and hit, while all your energy goes to policing her brother.

Both of those are the same feeling wearing different hats: you are one person doing a two-person job in the hardest fortnightly stretch of it. Your toddler isn’t broken and neither are you. He just needs the message to arrive in a language he can actually hear, which is what happens next, not what you say.