Why Your 15-Month-Old Isn’t Sleeping: The (Little-Known) Sleep Regression Explained

You thought you were in the clear.

Your little one had been sleeping pretty well—maybe even through the night. You finally felt like you had a rhythm. Bedtime wasn’t a total circus. You could predict their naps (most of the time). Maybe you were even staying up late to watch a show or drink a hot tea because, for once, you weren’t running on empty.

And then… it all changed. Again.

Suddenly, your 15-month-old is waking at random hours. Screaming the second you put them in the crib. Skipping naps they used to take like clockwork. Clinging to you during bedtime routine, only to throw their paci across the room once the lights go out.

You’re left wondering: What happened? Wasn’t the 12-month regression the last one? Why are we here again?

If that sounds familiar—take a deep breath. You’re not doing anything wrong. And no, you didn’t jinx yourself.

There is such a thing as a 15-month sleep regression. 🤯

It’s not as widely talked about as some of the others, but it can hit just as hard. And the good news is? It’s a phase, not forever.

This blog is here to give you the full scoop—why it happens, what to look for, and most importantly, how to navigate it without losing your mind (or your evening downtime).

Let’s unpack what’s going on. 👇

 1. Big Developmental Leaps Are Happening

Around 15 months, your little one is growing at lightning speed—physically, emotionally, and neurologically. Walking, climbing, babbling (or full-blown talking!), and problem-solving are all surging forward. Their brain is buzzing with activity, which can disrupt sleep, even if they’re clearly exhausted.

This sudden growth spurt is a big reason for 15-month-old sleep problems. The brain is overloaded, and while they’re eager to explore their new world, it can make bedtime feel like a battle.

 2. They’re Testing Boundaries

Yep, toddler sleep issues at 15 months are often linked to a stage where they start testing boundaries. Your toddler might suddenly resist bedtime routines or protest naps just to see what happens. This isn’t “bad behavior”—it’s normal, age-appropriate testing as they start learning cause and effect.

If you’re hearing bedtime battles like, “No night-night!” or they start full-body flailing when it’s time to get in the crib... you’re not alone. 15-month-old sleep regression can come with a ton of tantrums, and this is peak toddler energy.

 3. Separation Anxiety Peaks (Again)

Separation anxiety in toddlers often resurfaces at this age—and it’s tough. Your toddler may cry the second you leave the room or need extra cuddles at bedtime. This can feel heartbreaking, but it’s also a sign of secure attachment.

If you're deep in this phase, I highly recommend checking out my Separation Anxiety Blog. You’ll find lots of tips to help reduce bedtime crying and rebuild confidence for both of you.

🎧 Prefer to listen? Here's the podcast episode on Separation Anxiety.

 4. Teething Is No Joke

Let’s talk teeth. Around this age, many toddlers are cutting molars or working on several new teeth at once. Ouch. This discomfort can linger, interrupt sleep, and make them extra fussy or clingy. Some babies even wake early from naps or overnight due to teething pain.

Teething and sleep disruptions are common around 15 months, and the teething process can sometimes stretch over several weeks. For more info on teething and how it affects sleep, check out my Teething and Sleep Blog.

What to Do About the 15-Month Regression:

Here are a few things that help:

• Keep consistent routines, even if your toddler resists.

• Offer extra comfort at bedtime—but try to avoid creating new long-term sleep habits you don’t want to keep.

• Watch your wake windows! You want to try and avoid an overtired toddler as much as possible!

And most of all: take a deep breath. This phase can feel long and exhausting, but it will pass.

Need a Plan That Actually Works?

My Baby Sleep Course walks you through gradual, supportive steps to help your 15 Month old sleep longer stretches and fall asleep more independently.

You’ll learn how to handle bedtime battles, wake-ups, night weaning, and more!

✨ Get instant access to the course here.

You’ve got this mate!! And I’m right here cheering you on xx